Resurfacing arthroplasty in osteonecrosis of the hip

Approximately 10% of the total hip replacements performed in the United States are for osteonecrosis. Resurfacing arthroplasty has received renewed interest, with several new designs being implanted worldwide. Proponents of resurfacing arthroplasty describe the advantages of bone conservation, preservation of joint mechanics, more physiologic loading of the bone, lower incidence of perioperative complications, and easier conversion to a secondary procedure if failure occurs. Critics recite previous poor results including high failure rates with femoral and acetabular loosening, osteonecrosis of the femoral head, femoral neck fracture, and loss of acetabular bone stock making the secondary revision procedure more difficult. This article attempts to clarify the advantages and disadvantages of the resurfacing concept as it applies to the treatment of osteonecrosis of the femoral head.     

Removal of acetabular bone in resurfacing arthroplasty of the hip: a comparison with hybrid total hip arthroplasty

Resurfacing arthroplasty of the hip is being performed more frequently in the United Kingdom. The majority of these patients are younger than 55 years of age, and in this group the key benefits include conservation of femoral bone stock and the potential reduction in the rate of dislocation afforded by the larger resurfacing head. Early aseptic loosening is well recognised in patients younger than 55 years of age, and proponents of resurfacing believe that the improved wear characteristics of the metal-on-metal bearing may improve the long-term survival of this implant. There has been some concern, however, that resurfacing may not be conservative of acetabular bone.We compared a series of 33 consecutive patients who had a hybrid total hip arthroplasty with an uncemented acetabular component and a cemented femoral implant, with 35 patients undergoing a Birmingham hip resurfacing arthroplasty. We compared the diameter of the implanted acetabulum in both groups and, because they were not directly comparable, we corrected for patient size by measuring the diameter of the contralateral femoral head. The data were analysed using unpaired t-tests and analysis of covariance.There was a significantly larger acetabulum in the Birmingham arthroplasty group (mean diameter 56.6 mm vs 52.0 mm; p < 0.001). However, this group had a significantly larger femoral head diameter on the contralateral side (p = 0.03). Analysis of covariance revealed a significant difference between the mean size of the acetabular component implanted in the two operations. The greatest difference in the size of acetabulum was in those patients with a larger diameter of the femoral head. This study shows that more bone is removed from the acetabulum in hip resurfacing than during hybrid total hip arthroplasty, a difference which is most marked in larger patients.     

Comparison of Bone Removed During Total Hip Arthroplasty With a Resurfacing or Conventional Femoral Component : A Cadaveric Study

We sought to examine the amount of bone removed during total hip arthroplasty with a resurfacing femoral component, compared to with a conventional, stemmed femoral component, by using 6 male and 4 female cadaveric pelves with attached bilateral proximal femora. Using randomized assignment and order, a total hip arthroplasty with a resurfacing femoral implant was performed on one side, and total hip arthroplasty with a cementless, stemmed femoral implant was performed on the contralateral side. The relationship between native femoral head diameter and the implanted acetabular socket was on average within 2 mm for both procedures. No significant difference was observed in the amount of acetabular bone removed (9.8 g for hip resurfacing vs 8.8 g). However, a resurfacing component resulted in approximated 3 × less bone removal from the femur (25.8 g vs 75.1 g). This study shows that the preservation of femoral bone with a resurfacing femoral component does not result in an increased removal of acetabular bone when compared to the use of a conventional, stemmed femoral component.     

A study of implant failure in the Wagner resurfacing arthroplasty

Using clinical, radiographic, and pathological data, we investigated eighteen cases of early aseptic failure of an implant in patients who had undergone reconstruction of the hip with a Wagner resurfacing prosthesis. Sixteen patients required revision for loosening of the acetabular component, with eight of them also demonstrating loosening of the femoral component. One patient had loosening of the femoral component without failure of the acetabular component, and one patient sustained a femoral neck fracture that was associated with osteonecrosis. Six of the patients with loosening of the acetabular component had an associated significant loss of acetabular bone stock. Loosening was associated with the development of a membrane at the bone-cement interface in all patients. Histological examination of the membrane demonstrated a marked foreign-body response to wear products from the arthroplasty. Bone resorption appeared active at the bone-membrane interface. We concluded that the acetabular component of the Wagner prosthesis is prone to early loosening and that the early loosening is potentiated by a foreign-body response to debris resulting from arthroplastic wear.     

Femoral component neck fracture after failed hip resurfacing arthroplasty

Failure on the femoral side after third-generation metal-on-metal hip resurfacing arthroplasty is suggested to be easily treated with conversion to conventional total hip arthroplasty. Clinical results of conversion for failed hip resurfacing arthroplasty with the use of primary femoral implants confirmed this for a short-term follow-up. We present a case of the occurrence of a stemmed femoral implant neck fracture in a patient who was earlier treated for a failed hip resurfacing. We advise to consider acetabular revision in case of (suspected) acetabular metal damage and to use a stem component with a relative large neck diameter.     

Early acetabular protrusio following hemiresurfacing of the hip for osteonecrosis in sickle cell disease

A case report is presented of a patient with acetabular protrusio 2 years following hemiresurfacing of the femoral head for osteonecrosis associated with sickle cell disease. Renewed interest in bone-preserving hip arthroplasty has led to increased use of hemiarthroplasty and femoral resurfacing in young patients with arthritis. In cases of osteonecrosis, especially that associated with sickle cell disease, awareness of this potential complication is important.     

Metal-on-metal surface replacement: a triumph of hope over reason: affirms

Metal-on-metal hip resurfacing offers some potential for total hip arthroplasty (THA) in the young patient. However, short- and intermediate-term results of the currently available implants have failed to demonstrate advantage over conventional THA. The risks of femoral neck fracture or avascular necrosis have been disappointing early limitations of the procedure. The Australian Joint Registry reports a 5-year revision rate of all hip resurfacings of 3.8%, compared with conventional THAs at 2.8%, and a 9-year cumulative revision rate of 7.2% for hip resurfacings. Recent reports of femoral neck erosion and pseudotumors associated with resurfacing have raised concern about the survivorship of the procedure in some patients. Recently, the British Medicines and Healthcare Product Regulatory Agency issued an alert over adverse reactions associated with metal-on-metal THAs, with particular concern expressed about hip resurfacings. Acetabular bone stock may not be conserved when large-diameter femoral head components are used, depending on the surgical technique and implant design. In hip resurfacing, the minimum diameter femoral component avoids notching of the femoral neck; thus, larger diameter acetabular components may be necessary to accommodate the femoral component. Hip resurfacing is contraindicated in cases of avascular necrosis of the femoral head, especially with cysts >1 cm in diameter, with severe slipped capital femoral epiphysis, and in some posttraumatic arthroses; furthermore, the biomechanics of the resurfaced hip appear to be less reliably restored than with conventional THA. The hypothesis that resurfacing is a more conservative procedure than conventional THA remains unproven at this time. Given the documented intermediate failure rates of resurfacing, metal-on-polyethylene is the more successful implant choice.     

A randomised study comparing resection of acetabular bone at resurfacing and total hip replacement

We have undertaken a prospective, randomised study to compare conservation of acetabular bone after total hip replacement and resurfacing arthroplasty of the hip. We randomly assigned 210 hips to one of the two treatment groups. Uncemented, press-fit acetabular components were used for both. No significant difference was found in the mean diameter of acetabular implant inserted in the groups (54.74 mm for total hip replacement and 54.90 mm for resurfacing arthroplasty). In seven resurfacing procedures (6.8%), the surgeon used a larger size of component in order to match the corresponding diameter of the femoral component. With resurfacing arthroplasty, conservation of bone is clearly advantageous on the femoral side. Our study has shown that, with a specific design of acetabular implant and by following a careful surgical technique, removal of bone on the acetabular side is comparable with that of total hip replacement.     

Salvage of failed treatment of hip fractures

Typically, patients with failed internal fixation of a hip fracture have marked pain and disability. These patients may present treatment challenges. Salvage is tailored to the anatomic site of the nonunion, the quality of the remaining bone and articular surface, and patient factors such as age and activity level. In younger patients with either a femoral neck or intertrochanteric fracture nonunion with a satisfactory hip joint, treatment typically involves revision internal fixation with or without osteotomy or bone grafting. In older patients with poor remaining proximal bone stock or a badly damaged hip joint, conversion to hip arthroplasty can restore function effectively and reduce pain. For femoral head salvage procedures, choosing a fixation device and accurate preoperative planning are the major challenges in decision making. For conversion to arthroplasty, the major challenges are assessing the need for acetabular resurfacing, selecting the femoral implant, and managing the greater trochanter. Technical challenges include broken hardware, deformity, and femoral bone defects. Attention to technical details can minimize potential complications.     

Lack of radiographic loosening signs in a hip resurfacing that failed by stem fracture

Fracture of the femoral stem is a rare manifestation of femoral component loosening in hip resurfacing. The patient had undergone successful hip resurfacing 3 years prior to presentation, presenting with complaints of groin pain, but without radiographic evidence of loosening. At 6 years post-operatively, the patient again presented with groin pain. Radiographs demonstrated a mid-stem fracture. Analysis of the retrieved implant and resected femoral head following conversion to total hip arthroplasty indicated that component failure and fracture appeared to be secondary to failed fixation and implant loosening not related to osteonecrosis or acute femoral neck fracture. The case report highlights the difficulty in diagnosing femoral component loosening in hip resurfacing in the absence of gross implant subsidence or stem radiolucency.     

Revisionschirurgie des Oberflächenersatzes

Early results of contemporary hip resurfacing are encouraging and consequently an increasing number of this procedure has been performed worldwide. A theoretical advantage of hip resurfacing is that failed components can be revised safely and successfully revised to a conventional total hip arthroplasty. As the number of systematically analyzed failures is still limited, however, current data from the literature cannot substantially support this assumption.Our personal results indicate that the conversion of a failed femoral cup (i.e., due to neck fracture or aseptic loosening) to a conventional stem is a relatively simple and safe procedure. If and how potential wear of a firmly integrated acetabular component might have any impact on this type of revision, warrants further investigations.The conversion of acetabular components is influenced by the quality of the remaining pelvic bone stock and can therefore be compared to conventional revision surgery. However, as most providers of hip resurfacings systems only offer one-piece acetabular shells, the possibility of an isolated modular insert exchange is rare. In conclusion, the argument of easy revision surgery after hip resurfacing should be used with care.     

Total resurfacing for osteonecrosis of the hip

With the resurgence of metal-on-metal bearings, there is renewed interest in total hip resurfacing. A cementless acetabular component used for resurfacing with a wall thickness of fewer than 5 mm is comparable in size to acetabular components used for total hip replacement. The fixation of a porous-ingrowth acetabular component used for resurfacing has been shown to be reliable and durable. There are few clinical reports of total hip resurfacing that stratify results by diagnosis. However, available evidence indicates that the pain relief, function, and activity after total hip resurfacing for osteonecrosis are superior to the results reported for hemiresurfacing and similar to the results of total hip replacement. Femoral-side failure is the main issue occurring with total resurfacing for osteonecrosis, and the femoral side failure rate is higher than that of hemiresurfacing. There are no simple guidelines for the extent of femoral head necrosis that are compatible with successful resurfacing. Refined patient selection and surgical technique can improve the outcomes and durability of total hip resurfacing for osteonecrosis.     

Osteonecrosis in retrieved femoral heads after failed resurfacing arthroplasty of the hip

We present the histological findings of bone retrieved from beneath the femoral components of failed metal-on-metal hip resurfacing arthroplasties. Of a total of 377 patients who underwent resurfacing arthroplasty, 13 required revision; for fracture of the femoral neck in eight, loosening of a component in three and for other reasons in two. None of these cases had shown histological evidence of osteonecrosis in the femoral bone at the time of the initial implantation. Bone from the remnant of the femoral head showed changes of osteonecrosis in all but one case at revision. In two cases of fracture which occurred within a week of implantation, the changes were compatible with early necrosis of the edge of the fracture. In the remaining six fractures, there were changes of established osteonecrosis. In all but one of the non-fracture cases, patchy osteonecrosis was seen. We conclude that histological evidence of osteonecrosis is a common finding in failed resurfaced hips. Given that osteonecrosis is extensive in resurfaced femoral heads which fail by fracture, it is likely to play a role in the causation of these fractures.     

Outcome of hemiresurfacing in osteonecrosis of the femoral head

Hemiresurfacing of the femoral head for treatment of osteonecrosis has been proposed as a reasonable alternative to total hip arthroplasty. The results of 59 patients with Ficat Stage III osteonecrosis done by a single surgeon are reviewed. At an average followup of 4.5 years, 16 patients were considered failures because of conversion to total hip arthroplasty or considerable groin pain requiring medication. Failure did not correlate with age, body mass index, preoperative length of symptoms, acetabular articular cartilage status at the time of surgery, or cause of the underlying disease. The only factor associated with failure was a lower preoperative Harris hip score. Conversion of the failed implants to total hip arthroplasty was straightforward, confirming the conservative nature of the procedure. However, pain relief and recovery after resurfacing are less reliable than that associated with total hip arthroplasty. This procedure may be appropriate for patients younger than 30 years, given the ease of conversion to THR if failure occurs. The patient should be counseled regarding expectations.     

Biomechanische Aspekte zur Implantatverankerung und Kinematik von Oberflächenersatzhüftendoprothesen

Hip resurfacing is undergoing a resurgence in orthopaedic surgery with an increasing number of implantations. The objective of this article is to present the biomechanical basics of implant anchorage as well as the kinematics of hip resurfacing implants.Today, fixation of the femoral component onto the prepared femoral head is mainly done using bone cement. Depending on the implant design, the bone structures beneath the femoral component can be exposed to stress shielding, followed by degradation of the bone density and subsequent initiation of implant loosening. However, the trabecular bone has the ability to adapt itself to the fixation peg, to additional cement pegs, and to the elastic properties of the femoral component as well.The acetabular component is mainly inserted into the bone stock without using cement. Provided that large prosthetic heads will be applied, thin-walled acetabular cups are crucial for bone-saving preparation of the acetabular bone stock. Nearly all hip resurfacing systems are currently based on metal-on-metal wear-bearing couples. The acetabular components are mainly designed as monoblock implants, which can make subsequent revision difficult.Kinematic analyses show a significantly lower range of motion of hip resurfacing implants compared with modern standard (stemmed) total hip replacement systems. This difference originates from the small ratio of the resurfaced femoral head diameter and the relatively thick neck of the femur. Impingement of the femur neck onto the rim of the acetabular component can result in subluxation, deformation of the bearing surfaces, femoral neck fracture, and impairment of the bony anchorage of the hip resurfacing implants.     

Total hip arthroplasty in the treatment of developmental dysplasia of the hip

Total hip arthroplasty (THA) is the preferred treatment for patients with severe arthritis of the hip secondary to developmental hip dislocation or dysplasia. However, THA may be difficult due to bone and soft tissue problems that arise from hip dislocation or dysplasia. Another problem is that patients are usually young, which may affect the long-term survival of the prosthesis. Either cemented or uncemented components can be used depending on bone structure and bone stock. Uncemented components are more preferable because of the young age of the patients. From a biomechanical standpoint, the placement of the acetabular component in its true anatomical location is the main goal for survival and better functional results of THA. To ascertain the stability of the acetabular component, superior grafting, controlled medial wall perforation (medialization), or giving the position of a high hip center may be used. On the femoral side, various femoral components may be used with or without a shortening osteotomy. In this article, reconstruction options for developmental hip dysplasia are discussed depending on acetabular and femoral features of the deformity.     

Painful impingement of the hip joint after total hip resurfacing: a report of two cases

Many patients undergoing total hip resurfacing arthroplasty present with reduced anterior femoral neck concavity as a part of the degenerative process. Painful hip impingement may develop or persist after hip resurfacing when the retained femoral neck abuts against the metallic acetabular component or the anterior acetabular bony wall. We report on two cases of painful postoperative hip impingement after hip resurfacing, in one of whom anterior neck-contouring osteoplasty restored pain-free range of motion (ROM). To restore natural hip ROM, surgeons performing hip total hip resurfacing arthroplasty should aim to reproduce the normal femoral head-neck offset ratio. Femoral head-neck offset restoration can be achieved by proper femoral component positioning (especially optimal translation), by femoral neck osteoplasty or by increasing femoral component head size appropriately.     

Cup arthroplasty, surface replacement arthroplasty, and femoral head resurfacing for osteonecrosis

Traditional cup arthroplasty and resurfacing arthroplasty of the femoral head and acetabulum have been proposed as bone-conserving procedures for avascular necrosis of the hip. Resurfacing of only the femoral head is not a definitive procedure but is an alternative to cup arthroplasty and resurfacing arthroplasty of the femoral head and acetabulum; hemiarthroplasty is recommended for the young patient with intact acetabular cartilage. Indications, technique, and clinical results are presented.     

Total hip arthroplasty in sickle cell hemoglobinopathies

Advances in medical treatment have led to improved life expectancy in patients with sickle cell hemoglobinopathies. Improved life expectancy has, in turn, led to an increasing number of patients with osteonecrosis requiring total hip arthroplasty. Patient evaluation begins with understanding the extent of the disease process and the patient's musculoskeletal manifestations (ie, pyogenic infection, marrow hyperplasia, osteonecrosis). A multidisciplinary approach to implementing effective preoperative treatment strategies increases the likelihood of a successful surgical outcome. Intraoperatively, consideration of bone stock, bone quality, and method of component fixation may help minimize the risk of eccentric reaming, perforation or fracture of either the acetabulum or the femur, and loosening. The optimal mode of acetabular and femoral fixation in these patients has not been conclusively determined, but recent results of cementless total hip arthroplasty have been encouraging. Although patients with sickle cell disease are at increased risk of medical and surgical complications, total hip arthroplasty in the appropriately selected patient can provide significant pain relief, restoration of function, and patient satisfaction.     

Resurfacing arthroplasty. Femoral head viability

Although obvious theoretic advantages accrue from resurfacing arthroplasty of the hip, the indications for the procedure are controversial because the failure rate is high and loosening is unacceptably frequent. To determine the role of osteonecrosis in these failures, the viability of bone within the femoral head was determined by histologic examination of bone inside 25 failed femoral resurfacing components. The bone was substantially alive throughout the femoral head in 23 of 25 cases (92%). In two cases, the bone of the femoral head was dead. Both of these hips had clinically failed because of femoral neck fracture. This histologic evaluation indicates that bone death is not an inevitable consequence of femoral head resurfacing and the use of polymethylmethacrylate fixation.