Periacetabular osteolysis in association with well-fixed cementless components was first recognised as a serious clinical problem in the early 1990s. By the mid-1990s, revision surgery for pelvic osteolysis secondary to polyethylene wear was the most common revision hip procedure performed. As a result, new bearing surfaces were introduced in hopes of reducing wear volume and thus reducing pelvic osteolysis. These included highly crosslinked polyethylene, ceramic-on-ceramic and metal-on-metal bearing surfaces. Metal-on-metal has for the most part been eliminated in conventional hip replacement because of the concerns centered around adverse local tissue reactions. Both highly crosslinked polyethylene and ceramic-on-ceramic bearings have been successful in limiting wear and all but eliminating clinically significant osteolysis. Multiple reports on highly crosslinked polyethylene have documented wear rates below the lysis threshold. No reports of revision for wear have been reported despite twenty years of in-vivo use. Of import to the surgeons, all manufacturers commonly used in North America have performed well. In addition, highly crosslinked polyethylene has been relatively insensitive to head size allowing the use of 36mm femoral heads routinely. Similar reports are noted with ceramic-on-ceramic bearings. However, highly crosslinked has dominated the North American market because it is a relatively forgiving bearing surface and comes at a lower cost. Currently, there is a trend towards the use of ceramic femoral heads – not because of wear concerns, but concerns related to taper corrosion and large cobalt-chrome femoral heads.
The challenges faced by hip surgeons have changed over the last decade. Historically, fixation, polyethylene wear, osteolysis, loosening and failure to osseointegrate dominated the discussions at hip surgery meetings. With the introduction of highly crosslinked polyethylene, wear and osteolysis are currently not significant issues. Improved surgical technique has resulted in a high rate of osseointegration and once fixed, loosening of cementless components is rare. In this session, we will focus on issues that orthopaedic surgeons performing hip surgery routinely face including bearing couples in the young active patient, implant choices in the dysplastic hip and osteoporotic femur, evaluation and management of the unstable hip and differential diagnosis of the painful THR.
In North America, cementless femoral replacement has all but replaced cementing and cement technique is at risk for becoming a lost art. Published results of cemented femoral components with a well-designed femoral component and good surgical technique are excellent and equivalent to cementless technology. With an increasing focus on cost as part of value-based care, consideration for returning to cement for a select population is appropriate. Furthermore, there are patient populations that may benefit from a cemented femur with registries demonstrating superior short term outcomes. These include the elderly and patients with osteoporotic femurs. The goal of femoral cementing is to maximise the interdigitation of bone cement with metaphyseal trabecular bone and the irregular surface of the endosteum while at the same time minimizing the risk of embolization. The steps for femoral cementing include:cFemoral broaching – understand the relationship between the broach and stem as it relates to cement mantle thickness; Canal preparation; Gentle curetting to remove loose cancellous bone; Pressurised lavage to remove fat and marrow elements – this decreases the risk of embolization and enhances the strength of the bone-cement interface; Dry the canal – suction, adrenaline soaked sponge – this minimises bleeding and enhances the strength of the bone cement interface; Cement preparation – vacuum mix or centrifuge the bone cement – this minimise large voids that weaken the bone cement; Cement insertion – insert in a retrograde fashion and pressurise the cement – this optimises the cement column and the bone cement interface; Stem insertion – insert slowly with a system that centralises the stem – this prevents mantle defects that have been associated with stem loosening.
Contemporary polyethylene liners for total hip replacements were introduced in the late 1990's to address osteolysis associated with wear of conventional polyethylene. Every major device manufacturer introduced an “enhanced polyethylene”. In the ensuing decade plus, every major arthroplasty meeting had presentations and debates about the wear resistance and mechanical properties of these new polymers. The results have been remarkable and now with 17 to 18 years of use in patients, we have yet to see clinically significant osteolysis in our patients regardless age or activity level. The results can be summarised as follows: All currently commercially available highly crosslinked polyethylenes produced by major device companies have demonstrated a reduction in wear and osteolysis. At the 2016 Closed Meeting of The Hip Society, none of the surgeons attending had seen a clinically significant case of osteolysis associated with highly crosslinked polyethylene. Registry data demonstrates the superiority of the highly crosslinked materials over conventional polyethylenes. Historical concerns over a reduction in mechanical properties have not been borne out in clinical studies. Although highly crosslinked polyethylene liner fractures have been reported, they are rare and probably related to specific designs or surgical technique issues. It is important to remember that there were rare cases of fracture of conventional polyethylene as well. With currently reported wear rates of the enhanced polyethylenes, polyethylene thickness is unlikely to be a factor in long-term durability with well-designed sockets. Bench data has demonstrated that polyethylene thickness is not a risk factor for wear or fracture if well supported by the metal shell. Thin unsupported polyethylene is at risk for fracture. Although the new anti-oxidant polyethylenes (eg. Vitamin E) have performed well in wear studies, there is no clinically available evidence to support their use based on enhanced fracture toughness.
The challenges faced by hip surgeons have changed over the last decade. Historically, fixation, polyethylene wear, osteolysis, loosening and failure to osseointegrate dominated the discussions at hip surgery meetings. With the introduction of highly crosslinked polyethylene, wear and osteolysis are currently not significant issues. Improved surgical technique has resulted in a high rate of osseointegration and once fixed, loosening of cementless components is rare. In this section, we will focus on issues that orthopaedic surgeons performing hip surgery routinely face including bearing couples in the young active patient, implant choices in the dysplastic hip and osteoporotic femur, evaluation and management of the unstable hip and differential diagnosis of the painful THR.
A standard is defined as something established by authority, custom, or general consent. Clearly that does not exist for ceramic on ceramic total hip replacement. A better question is: Is there any indication for a ceramic on ceramic total hip. The answer to that question should when possible be based on clinical outcome data including the value added (or not) with this more expansive technology. Ceramic on ceramic has been popularised based on its low wear. Is this clinically relevant? Probably not, based on currently available data. Both metal on highly crosslinked polyethylene and ceramic on highly crosslinked polyethylene have very low clinically documented wear rates with excellent outcomes in multiple studies. In addition, ceramic on ceramic bearings are more sensitive to implant position. Whereas polyethylene may tolerated edge loading and impingement, ceramic bearings are less likely to do so. Dislocation remains one of if not the top reason for early revision. Even with newer ceramics, there are still less options to fine tune hip stability with ceramic on ceramic bearing surfaces. When looking at the overall, risk of revision, Bozic et al concluded that hard bearings provided no benefit in terms of risk reduction of revision. Considering their higher cost, they questioned the use of these products especially in the 65 and older age group. Looking at the Australian Registry, the cumulative percent revision for ceramic-ceramic THA was 5.7% at 11 years compared to 5.1% for metal on crosslinked poly. The hazard ratio (adjusted for age and gender) was 1.09 in favor of ceramic on poly and the difference was highly significant (p=0.012). When one take into account the increased cost of ceramic on ceramic bearings, it is hard to make a case for ceramic on ceramic bearings. Any use of ceramic on ceramic bearings would have to be based on the hypothesis that in the long run in young active patients they may provide an advantage. This is a hypothesis with no data to support it currently.
With cementless porous-coated acetabular replacements, extensive bone loss can occur without effecting implant stability. As a result, the surgeon is frequently faced with re-operating on a well-fixed cementless acetabular component with osteolysis and must decide whether or not to remove a well-fixed porous coated socket. A classification system and treatment algorithm has been developed to aid in management decisions regarding re-operation for polyethylene wear and pelvic osteolysis. Cases are classified into one of 3 possible categories depending on the radiographic stability of the porous coated shell and the ability to replace the polyethylene liner. Type I case; stable porous coated shell, liner replaceable; Type II case; socket stable, liner not replaceable; Type III case; socket loose, not osseointegrated. Treatment Algorithms - Retain well-fixed shell in Type I cases and replace the liner. Debride accessible lytic lesions and graft with allograft chips. Remove the well-fixed shell in Type II case. Assess defect once the shell is removed. Reconstruction based on the bony defect present. The vast majority can be revised with a larger porous coated socket. Remove loose socket in Type III cases. Assess defect and reconstruct based on the defect. There is a greater need for more extensive grafting and the use of reconstruction rings with Type III cases. This treatment algorithm has helped the authors successfully evaluate and treat a large series of patients with polyethylene wear and pelvic osteolysis in association with porous coated acetabular components. The stability of the acetabular component and appropriate knowledge of the implant are important factors that impact surgical management.
Outcome in total hip replacement is influenced by a variety of factors including patient selection, implant technology, surgical expertise and peri-operative management. As it relates to the direct anterior approach, there has been extensive marketing in order to drive patients to specific surgeons who use specific implants. Associated with this marketing, claims about superiority of this approach have been made with very little evidence to support these claims. In a study comparing the direct anterior (DA) to the miniposterior approach, Pagnano et al showed no difference in length of stay, operative complications, IV breakthrough analgesia, stairs, maximum feet walked in hospital or percent discharged to home. The DA approach had longer operative times, higher maximum visual analog pain score and at two weeks more of the DA group required gait aids. At eight weeks the DA group had a higher Harris Hip Score but lower return to work and driving. They concluded no advantage of the DA approach. Even when comparing the DA approach to the conventional posterior approach Ranawat et al were only able to identify some benefit at 2 weeks which had disappeared by 6 weeks. Finally in a randomised prospective trial Taunton et al demonstrated very little differences between the DA and miniposterior approaches. The DA group time to ambulation without aids was slightly better in the DA group (22 vs. 28 days) and the three week SF mental scores were slightly better in the miniposterior group. They concluded little clinical or radiographic benefit was seen between the cohorts. The evidence suggests if done well both approaches work well. The key to long term success is to get the parts in write regardless of approach.
With cementless porous-coated acetabular replacements, extensive bone loss can occur without affecting implant stability. As a result, the surgeon is frequently faced with re-operating on a well-fixed cementless acetabular component with osteolysis and must decide whether or not to remove a well-fixed porous coated socket. A classification system and treatment algorithm has been developed to aid in management decisions regarding re-operation for polyethylene wear and pelvic osteolysis. Cases are classified into one of 3 possible categories depending on the radiographic stability of the porous coated shell and the ability to replace the polyethylene liner. Type I case; stable porous coated shell, liner replaceable; Type II case; socket stable, liner not replaceable; Type III case; socket loose, not osseointegrated Relative Contra-indications for Liner Exchange – Type II Case - Malpositioned socket, Severely damaged shell or lock detail (consider cementing shell in place), Poor track record of the implant, Highly crosslinked polyethylene liner of adequate thickness not available, Ongrowth (as opposed to ingrowth) fixation surface Treatment Algorithm Type I Case: Retain well-fixed shell in Type I cases and replace the liner. Debride accessible lytic lesions and graft with allograft chips. Type II Case: Remove the well-fixed shell in Type II case. Assess defect once the shell is removed. Reconstruction based on the bony defect present. The vast majority can be revised with a larger porous coated socket. Type III Case: Remove loose socket. Assess defect and reconstruct based on the defect. There is a greater need for more extensive grafting and the use of reconstruction rings with Type III cases. This treatment algorithm has helped the authors successfully evaluate and treat a large series of patients with polyethylene wear and pelvic osteolysis in association with porous coated acetabular components. The stability of the acetabular component and appropriate knowledge of the implant are important factors that impact surgical management.
This session will be practically oriented, focusing on important surgical decisions and on technical tips to avoid complications. The panel will be polled concerning individual preferences as regards the following issues in primary total hip arthroplasty: Peri-operative antibiotics/blood management/preferred anesthetic, Surgical approach for primary total hip arthroplasty: indications or preferences for direct anterior, anterolateral, posterior, less invasive exposures, Acetabular fixation, Tips for optimising acetabular component orientation, Femoral fixation: Indications for cemented and uncemented implants and Role of hip resurfacing, Preferred femoral head size, Choice of bearing surface, Tips for optimising intra-operative hip stability, Tips for optimising leg length, Post-operative venous thromboembolism prophylaxis, Heterotopic bone prophylaxis, Post-operative pain management, rehabilitation protocol, activity restrictions and antibiotic prophylaxis.
