Introduction and Aims: The incidence and technical complexity of revision total hip arthroplasty (THA) has and will continue to increase dramatically. We report the results of revision THA using a non-cemented, dual threaded, cone shaped, (DTCS) modular femoral component. Method: Between June of 1999 and July of 2003, 41 revision THAs using a DTCS modular femoral component. Fifty-four percent of the patients were male and 46% were female with an average weight of 84kg (std dev: 30kg, range 57–60 kg), an average height of 170cm (sdt dev: 9cm, range: 155–182 cm) and an average body mass index (BMI) of 26 (std dev: 4, range: 18–31). The average patient age was 71 years (std dev: 12 years, range: 39–85 years). Results: The average patient follow-up was 16 months (range 6–49 months). The average Harris hip score (HHS) at the most recent time to follow-up was 76. Broken into the HHS component parts, the average pain score was 40 of a possible 44, average motion was nine of a possible nine, and average function was 28 of a possible 47. Radiographic evaluation revealed wellfixed and positioned components with evidence of bone densing in areas in intimate contact with the DTCS component. Radiographic evidence of minor stress shielding was observed in the greater trochanter (Gruen Zone 1) and the proximal calcar/neck cut region (Gruen Zone 7). Post-operative complications included recurrent infection in four (10%), subsequently resolved with IV antibiotics; dislocation in three (7%), successfully treated by closed reduction and protective bracing; aseptic loosening in one (2%), with femoral component revision to a larger size; intra-operative periprosthetic fracture in one (2%), treated with ORIF (bone, plate and screws); and a non-union of a pre-revision fracture with subsequent component loosening in one (2%). Regardless of the degree of femoral deficiency, there was no incidence of component disassociation or component fracture. Conclusion: Revision THA is a demanding undertaking and involves multivariate technical challenges that may include mechanical and material considerations such as prosthetic loosening, prosthetic and periprosthetic fracture. We show that the use of a DTCS modular femoral component affords the surgeon results equal to those reported for revision THA and allows intra-operative versatility independent of bone quality

Modularity of femoral components has been widely accepted at the head neck junction, most commonly combining two unlike metals with only sporadic reporting of compatibility issues and corrosion. The development and introduction of a new and improved modular neck junction (Rejuvenate Modular Femoral component, Stryker Orthopedics) provided the option of fine-tuning leg lengths, offset and stability. The surgical technique did indeed provide the desired endpoints, however, the early recognition of problems with the junction causing corrosion and Adverse Local Soft Tissue Reaction (ALTR) and subsequent revision has led to the product being voluntarily withdrawn from the market. My experience as an early user of this stem is described in this manuscript providing a better early recognition and treatment of this potentially very destructive process. Methods. A retrospective review of one hundred and ninety one Rejuvenate Stems that were implanted between January 2010 and January of 2012. However, after March 2011, this stem was only used on those patients who had a rejuvenate stem on the contralateral side. They were all implanted through a mini posterior incision with the first 82 patients receiving a Tritanium cluster hole cup (Stryker Orthopedics) with between two and three screws. The remaining 109 patients had an ADM (Anatomic Dual Mobility, Stryker Orthopedics). All patients were allowed to bear weight as tolerated and were followed up with Xrays at six weeks and one year. Clinical visits were recorded at 2 weeks and 6 months postop. Additional follow up was scheduled every two years following the first annual visit. Results. One hundred and seventy four of the 191 hips were available for review at the one-year follow-up. Fourteen patients have undergone revision of the hip due to increased pain and formation of an avascular pseudo capsule due to corrosion at the neck stem junction. All patients have demonstrated a black flaky residue at the taper junction and all have had a large, tense effusion with a milky colored fluid. A neo caspsule has formed in all patients that appeared avascular and thickened. Seven of the eight tritanium cups in the revision cases were loose and required revision, while none of the ADM cups were loose. One patient has undergone two revisions since the initial cause of failure was not recognized and she subsequently developed pain within three months following placement of a new modular neck at the initial revision. One patient who underwent revision developed a deep infection and is currently on antibiotics but has not cleared the infection as of this writing. Conclusion. There has been catastrophic early failure of a modular femoral component due to corrosion at the neck stem junction during the very early stages of follow up. An intense reaction appears to begin early on, perhaps contributing to failure of bony ingrowth in certain cup designs but not others. Patients who develop early onset of discomfort progress to a poorly functioning hip that presents with pain, swelling and decreased ROM. These patients need to be assessed with serum ion levels, joint aspiration for infection and ion levels if possible. A MRI with MARS technology is useful in identifying joint fluid and neo caspsule expansion. These patients should be advised on the adverse reaction that can develop and revision of the hip should be expeditiously carried out

There is increasing global awareness of adverse reactions to metal debris and elevated serum metal ion concentrations following the use of second generation metal-on-metal total hip arthroplasties. The high incidence of these complications can be largely attributed to corrosion at the head-neck interface. Severe corrosion of the taper is identified most commonly in association with larger diameter femoral heads. However, there is emerging evidence of varying levels of corrosion observed in retrieved components with smaller diameter femoral heads. This same mechanism of galvanic and mechanically-assisted crevice corrosion has been observed in metal-on-polyethylene and ceramic components, suggesting an inherent biomechanical problem with current designs of the head-neck interface.

We provide a review of the fundamental questions and answers clinicians and researchers must understand regarding corrosion of the taper, and its relevance to current orthopaedic practice.

Cite this article: Bone Joint J 2016;98-B:579–84.

Aims. We evaluated a large database with mechanical failure of a single uncemented modular femoral component, used in revision hip arthroplasty, as the end point and compared them to a control group treated with the same implant. Patient- and implant-specific risk factors for implant failure were analyzed. . Methods. All cases of a fractured uncemented modular revision femoral component from one manufacturer until April 2017 were identified and the total number of implants sold until April 2017 was used to calculate the fracture rate. The manufacturer provided data on patient demographics, time to failure, and implant details for all notified fractured devices. Patient- and implant-specific risk factors were evaluated using a logistic regression model with multiple imputations and compared to data from a previously published reference group, where no fractures had been observed. The results of a retrieval analysis of the fractured implants, performed by the manufacturer, were available for evaluation. Results. There were 113 recorded cases with fracture at the modular junction, resulting in a calculated fracture rate of 0.30% (113/37,600). The fracture rate of the implant without signs of improper use was 0.11% (41/37,600). In 79% (89/113) of cases with a failed implant, either a lateralized (high offset) neck segment, an extralong head, or the combination of both were used. Logistic regression analysis revealed male sex, high body mass index (BMI), straight component design, and small neck segments were significant risk factors for failure. Investigation of the implants (76/113) showed at least one sign of improper use in 72 cases. Conclusion. Implant failure at the modular junction is associated with patient- and implant-specific risk factors as well as technical errors during implantation. Whenever possible, the use of short and lateralized neck segments should be avoided with this revision system. Implantation instructions and contraindications need to be adhered to and respected. Cite this article: Bone Joint J 2020;102-B(5):573–579

Introduction: The S-ROM. ®. modular hip system (DePuy, Warsaw, IN) has a cementless femoral component made of titanium alloy with a distally fluted and slotted stem. The stem mates with a sleeve that is implanted in the proximal femur. No reports exist in the literature of intraoperative difficulties in disengaging the sleeve-stem interface. Induced by the impossibility of intraop-eratively disconnecting the sleeve-stem interface in one patient leading to unintended revision of a well-fixed sleeve, we asked whether in vivo evidence for fretting or mechanically-assisted crevice corrosion of the mating surfaces could be found in retrieved components and whether its appearance is influenced by factors such as length of implantation. Methods: The sleeve-stem combinations were retrieved from 1998 to 2008 as part of our IRB-approved implant retrieval system. Twenty-two sleeve-stem interfaces of S-ROM. ®. femoral components were located in our retrieval collection. Seven sleeve-stem combinations were still mated when retrieved; 2 were disengaged by hammering the sleeve away from the stem, the remaining 5 had to be cut longitudinally with a diamond saw to disengage the sleeve from the stem. All disengaged sleeves were also cut to expose their inner surfaces. The surfaces of the taper region and the corresponding inner surfaces of the split sleeves were inspected macroscopically and assigned to the following groups: severe corrosion; moderate surface changes; and few or no evidence of surface changes. Microscopic examination was used to grade fretting and corrosion using an established subjective scale (Goldberg et al., 2002). The surface of the taper and the sleeve was divided into 12 regions each and every region was evaluated separately. The mean score of all 24 regions was calculated and opposed to the implantation time of the respective femoral component. Statistical analysis of correlation between the mean score and implantation length was performed using the Pearson product moment correlation. Additionally, the surface of the taper regions of 6 specimens underwent detailed analysis with SEM and EDAX. Results: In 3 of 22 sleeve-stem interfaces severe corrosion accounting for at least 80% of the surface area was detected. Furthermore, ten sleeve-stem interfaces showed moderate surface changes. Nine sleeve-stem interfaces showed few or no surface changes. There was no correlation between presence of corrosion and implantation length (r=0.13; p=0.56). Conclusion: In 3 of 22 retrieved sleeve-stem interfaces severe corrosion was found at the stem-sleeve interface. Though apparently not the rule, failure to disengage the stem from the sleeve undermines an important advantage of this type of modularity in total hip replacement and suggests that alternative procedures should be anticipated when planning for revision surgery of such (or a similar) modular femoral component

Total hip replacement for developmental hip dysplasia is challenging. The anatomical deformities on the acetabular and femoral sides are difficult to predict. The Crowe classification is usually used to describe these cases – however, it is not a very helpful tool for pre-operative planning. Small acetabular components, acetabular augments, and modular femoral components should be available for all cases. Regardless of the Crowe classification, the surgeon must be prepared to perform a femoral osteotomy for shortening, or to correct rotation, and/or angulation. Cite this article: Bone Joint J 2013;95-B, Supple A:31–6

We report the minimum five-year follow-up of 352 primary total hip replacements using the uncemented hydroxyapatite-coated ANCA-Fit femoral component with a modular neck and head. The series comprised 319 patients (212 men, 107 women) with a mean age at operation of 64.4 years (28 to 97). The principal diagnosis was osteoarthritis. A total of 18 patients (21 hips) died before their follow-up at five years, nine patients (11 hips) were lost to follow-up, and four (four hips) declined further follow-up. Patient-reported outcomes have been recorded for 288 patients (316 hips).

Their mean Oxford Hip Score improved significantly from 41 points (16 to 57) pre-operatively to 20 points (12 to 44) at five-year follow-up. Radiological assessment showed good bony stability in 98% of implants. There were two cases of aseptic loosening of the femoral component. There were no clinical or radiological complications related to modularity. In our series we did not see the high rate of intra-operative fracture previously reported for this implant.

This medium-term follow-up study demonstrates that the clinical outcome of the ANCA-Fit femoral component is, to date, comparable with that of other metaphyseal loading femoral components.

Purpose

In revision hip surgery, Type IIIB femurs have presented the greatest historical challenge to achieving stable fixation and osseous integration. This study evaluated the intermediate term outcome of a modular, tapered, distal fixation revision femoral component used in a consecutive revision hip series with special attention to its performance in the defective Type IIIB femur.

Revision total hip arthroplasty (THA) is challenging when there is severe loss of bone in the proximal femur. The purpose of this study was to evaluate the clinical and radiographic outcomes of revision THA in patients with severe proximal femoral bone loss treated with a fluted, tapered, modular femoral component. Between January 1998 and December 2004, 92 revision THAs were performed in 92 patients using a single fluted, tapered, modular femoral stem design. Pre-operative diagnoses included aseptic loosening, infection and peri-prosthetic fracture. Bone loss was categorised pre-operatively as Paprosky types III-IV, or Vancouver B3 in patients with a peri-prosthetic fracture. The mean clinical follow-up was 6.4 years (2 to 12). A total of 47 patients had peri-operative complications, 27 of whom required further surgery. However, most of these further operations involved retention of a well-fixed femoral stem, and 88/92 femoral components (97%) remained in situ. Of the four components requiring revision, three were revised for infection and were well fixed at the time of revision; only one (1%) was revised for aseptic loosening. The most common complications were post-operative instability (17 hips, 19%) and intra-operative femoral fracture during insertion of the stem (11 hips, 12%). Diaphyseal stress shielding was noted in 20 hips (22%). There were no fractures of the femoral component. At the final follow-up 78% of patients had minimal or no pain. . Revision THA in patients with extensive proximal femoral bone loss using the Link MP fluted, tapered, modular stem led to a high rate of osseointegration of the stem at mid-term follow-up. Cite this article: Bone Joint J 2015; 97-B:312–17

Introduction and Aims: Currently, multiple femoral component types and sizes exist for primary total hip arthroplasty. However, component sizes for small femoral geometry are generally not available. The purpose of this study is to present the short-term use of a femoral component with sizes that extend into small femoral morphometry applications. Method: Between November 2001 and December 2003, 20 primary THA cases and three revision THA cases were performed utilising a non-cemented, dual threaded, cone shaped (DTCS) modular femoral component manufactured in off-the-shelf sizes, which include those sizes for small femora. The components are made of CoCr and include a size ‘Z’ (19mm proximal, 9mm distal) and a size ‘Y’ (17mm proximal, 8mm distal). Both components have hydroxyapatite coating for stimulating increased bone on-growth and a modular neck allowing intra-operative adjustments of leg length, version, offset and neck length. Results: The average patient follow-up was 10 months (range 64 days to 27 months). There were 19 (83%) hips in which the ‘Z’ component was used, and four (17%) hips with the ‘Y’ component. Radiographic evaluation revealed well-fixed and positioned components with evidence of bone densing in areas in intimate contact with the DTCS component. Radiographic evidence of minor stress shielding was observed in the greater trochanter (Gruen Zone 1) and the proximal calcar/neck cut region (Gruen Zone 7). Two revision cases (8%) required the additional use of a 6cm modular extension component (MEC) to bridge a proximal femoral deficiency. Two cases (8%) required adjunctive strut allografting at the time of surgery to protect a thin or deficient femoral cortex. There were no reported postoperative complications related to the femoral component. There was no disassociation of the modular neck from the femoral stem and there was no incidence of femoral component fracture. Conclusion: While expanding component profile offerings into larger sizes is common, developing similar component designs for abnormally small femora is uncommon, beyond the scope of the materials used and only done as a ‘custom’ order. The DTCS modular femoral component used affords a versatile option when presented with cases involving small femoral morphometry. We conclude that the DTCS component in smaller sizes is promising and warranted for continued use

The aim of this study was to assess the effect of frictional torque and bending moment on fretting corrosion at the taper interface of a modular femoral component and to investigate whether different combinations of material also had an effect. The combinations we examined were 1) cobalt–chromium (CoCr) heads on CoCr stems 2) CoCr heads on titanium alloy (Ti) stems and 3) ceramic heads on CoCr stems. In test 1 increasing torque was imposed by offsetting the stem in the anteroposterior plane in increments of 0 mm, 4 mm, 6 mm and 8 mm when the torque generated was equivalent to 0 Nm, 9 Nm, 14 Nm and 18 Nm. In test 2 we investigated the effect of increasing the bending moment by offsetting the application of axial load from the midline in the mediolateral plane. Increments of offset equivalent to head + 0 mm, head + 7 mm and head + 14 mm were used. Significantly higher currents and amplitudes were seen with increasing torque for all combinations of material. However, Ti stems showed the highest corrosion currents. Increased bending moments associated with using larger offset heads produced more corrosion: Ti stems generally performed worse than CoCr stems. Using ceramic heads did not prevent corrosion, but reduced it significantly in all loading configurations. Cite this article: Bone Joint J 2015;97-B:463–72

We retrospectively reviewed 161 revision THAs with diaphyseal fitting, mid- modular femoral components performed by ten surgeons at two academic medical centers. The average follow-up was 6.1 years. At final follow-up, 4 patients required re-revision for failure of the femoral component; 3 (2%) for aseptic loosening and 1 for mechanical failure of stem in setting of periprosthetic fracture. There were a total of 24 (14.9%) revisions for any reason, with the most common reason being septic failure (10 of 24). To our knowledge, this is the largest reported series of mid-term survivorship and complications of revision THA with mid-modular femoral components. Our results show that these stems have a low rate of aseptic loosening, subsidence, and mechanical failure

Uncemented metal-on-polyethylene total hip arthroplasties (THAs) have had a modular cobalt-chrome alloy head since their introduction in the early 1980's. Retrieval analysis studies and case reports in the early 1990's first reported corrosion between the femoral stem trunnion (usually titanium alloy) and cobalt-chrome alloy femoral head. However, then this condition seemed to disappear for about two decades? There are now numerous recent case series of this problem after metal-on-polyethylene THA, with a single taper or dual taper modular femoral component. Metal ion elevation, corrosion debris, and effusion are caused by mechanically assisted crevice corrosion (MACC). These patients present with diffuse hip pain, simulating trochanteric bursitis, iliopsoas tendinitis, or even deep infection. Trunnion corrosion, with adverse local tissue reaction, is a diagnosis of exclusion, after infection, loosening, or fracture. The initial lab tests recommended are: ESR, CRP, and serum cobalt and chromium ions. With a metal-on-polyethylene THA, a cobalt level > 1ppb is abnormal. Plain radiographs are usually negative, but may show calcar osteolysis or acetabular erosion or cyst. MARS MRI may be the best imaging study to confirm the diagnosis. Hip aspiration for culture and cell-count may be necessary. The operative treatment is empiric, with debridement, and head exchange with a ceramic head-titanium sleeve (or oxidised zirconium head) placed on the cleaned trunnion. The femoral component may have to be removed if there is “whole trunnion failure”. This usually relieves the symptoms, but the complication rate of this procedure may be high

Distal neck modularity places a modular connection at a mechanically critical location, which is also the location that confers perhaps the greatest clinical utility. The benefits of increased clinical options at that location must be weighed against the potential risks of adding an additional junction to the construct. Those risks include prosthetic neck fracture, taper corrosion, metal hypersensitivity, and adverse local tissue reaction. Further, in-vitro testing of ultimate or fatigue strength of femoral component designs has repeatedly failed to predict behavior in-vivo, raising questions about the utility of in-vitro testing that does not incorporate the effect of mechanically assisted crevice corrosion into the test design. The material properties of Ti alloy and CoCr alloy place limits on design considerations in the proximal femur. The smaller taper junctions that are necessary for primary reconstruction are particularly vulnerable to failure whereas larger taper junctions commonly used in revision modular femoral component designs have greater opportunity for success. Modular junctions of CoCr alloy on conventional Ti alloy have been shown to have a greater incidence of clinically significant mechanically assisted crevice corrosion and adverse reaction. Designs that have proven clinical strength and utility universally have larger, more robust junctions, that extend into the metaphysis of the femur. While these designs are primarily designed for revision total hip replacement (THR), they are occasionally indicated for primary THR. Overall, however, while design options at the neck-stem junction have unmatched clinical utility, no design that does not extend into the metaphysis has proven to be universally reliable. While routine use of modular neck components for primary THR does not appear to be clinically indicated based on current evidence, modular designs with proven successful proximal junctions appear to be indicated for revision THR and rare primary THR with extreme version or other anatomical circumstances

Two-stage revision arthroplasty is the gold standard for treatment of infection after total hip Arthroplasty and end stage septic arthritis of the hip. In the first stage we used a modified technique to insert an inexpensive modular femoral component coated with antibiotic-impregnated polymethylmethacrylate articulating with a polyethylene liner. The construct was used in 8 patients with infected arthroplasty, and 6 patients with septic arthritis of the hip. Two patients were excluded (no second stage). Of the remaining 12 patients, only one patient had persistent infection after the first stage; 11 patients received a successful re-implantation at the second-stage. The technique provide a construct that can be used safely and successfully in the awaiting period between the two stages of revision arthroplasty

The endoprosthetic treatment of secondary osteoarthritis resulting from congenital hip dysplasia is difficult due to the small diameter of the acetabulum and the hypoplastic anterolateral bone stock. On the femoral side the increased femoral anteversion, insufficient femoral offset and proximal femoral deformities (mostly valgus deformities) as well as the small diameter and straight form of the intramedullary canal pose challenges. Careful preoperative planning is mandatory. The Crowe classification is usually used to describe these pathologies. In severe cases (Crowe 3 and especially Crowe 4) a shortening and derotating femoral osteotomy should be taken into account. Small acetabular components, acetabular augments, and modular femoral components must be available at all times. For acetabular fixation press-fit cups are preferred today, but excellent results were also described for threaded cups. The advantage of press-fit cups is the extensively documented and superior track record, but threaded cups allow for an easier reconstruction of the original hip center as well as slight medialization. As a result of medialization a reduction in polyethylene wear together with a low rate of loosening lead to very good long-term results in a younger patient population. Cementless straight stems are documented to be preferable for the small femoral diameter and the straight anatomic shape of the proximal femur. Nevertheless, the higher complication rate, especially the increased rate of nerve palsies, should be preoperatively discussed with the patient. The ideal bearing surface is currently unclear, ceramic-on-ceramic seems to be promising, although the longest data available support the use of metal-on-polyethylene

We present a series of 30 uncemented total hip replacements performed between June 1985 and January 2002 with a mean follow-up of seven years (5 to 20) in 27 patients who had previously undergone a valgus intertrochanteric osteotomy. No further osteotomy was undertaken to enable hip replacement. We used a number of uncemented modular or monoblock femoral components, acetabular components and bearings. The patients were followed up clinically and radiologically. We report 100% survival of the femoral component. One acetabular component was revised at five years post-implantation for aseptic loosening. We noted cortical hypertrophy around the tip of the monoblock stems in six patients. We believe that modular femoral components should be used when undertaking total hip replacement in patients who have previously undergone valgus femoral osteotomy

Background. Modular component options can assist the surgeon in addressing complex femoral reconstructions in total hip arthroplasty (THA) by allowing for customization of version control and proximal to distal sizing. Tapered stem fixation has a proven excellent track record in revision THA. Early reports by Cherubino et al. (Surg Technol Int 2010) 65 revision THA with an average follow up of 109 months (range, 76–131) demonstrate satisfactory integration in 100% of cases. Rodriguez et al.(J Arthroplasty 2009) report 96% survival in 102 revision THA at nearly 4 years average follow up. We review the early clinical results of a modular tapered femoral revision system. Methods. A query of our practice's arthroplasty registry revealed 60 patients (61 hips) who signed an IRB-approved general research consent allowing retrospective review, and underwent THA performed with the modular femoral revision system between December 2009 and April 2012. There were 35 men (58%) and 25 women (42%). Mean age was 65.1 years (range, 35–94) and BMI was 31.3 kg/m2 (range, 14–53). Procedures were complex primary in 1 hip, conversion in 6 (10%), revision in 32 (53%), and two-staged exchange for infection in 22 (33%). Two-thirds of the procedures included complete acetabular revision (n=40), while 31% (19) involved liner change only and 2 were isolated femoral revisions. Results. At an average follow-up of 1.5 years (maximum: 3.7 years) there have been no revisions or failures of the femoral component. Average Harris hip scores (0 to 100 possible) improved from 44.2 preoperatively to 66.0 at most recent evaluation, while the pain component (0 to 44 possible) improved from 15.8 to 31.2. Complications requiring surgical intervention included intraoperative periprosthetic femur fracture in one patient returned to the operating suite same day for open reduction internal fixation, which further required incision and debridement for superficial infection at 1 year postoperative; and two patients with dislocation and fracture of the greater trochanter treated with open reduction, revision of the head and liner, and application of cerclage cables, one of which required removal of a migrated claw 10 months later followed 2 weeks subsequently with incision and debridement for a non-healing wound. Postoperative radiographs were available for review for 59 THA in 58 patients. Analysis of the femoral component revealed satisfactory findings in 50 hips (85%) while 9 had radiographic changes that included bone deficit, osteolysis, or radiolucency in one or more zones. Conclusions. The early results of this modular femoral revision system are promising for the treatment of the deficient femur in complex primary and revision total hip arthroplasty. Patients with radiographic changes are advised to return for regular clinical and radiographic follow-up. Survival of the modular femoral component in this series was 100% at mean follow-up of 1.5 years and up to 3.7 years. While Harris hip clinical and pain scores were somewhat low at most recent evaluation, they were significantly improved over preoperative levels

Arthritis of the hip is a relatively common problem in patients with neuromuscular disorders due to muscle imbalance around the hip from weakness, paralysis, contractures and spasticity. Neuromuscular disorders such as cerebral palsy, Parkinson's disease, poliomyelitis, previous cerebrovascular accident (CVA) and Charcot arthropathy have been considered by many to be contraindications to total hip arthroplasty (THA). The presence of certain anatomic abnormalities (excessive femoral anteversion, acetabular dysplasia, leg length discrepancy (LLD) and coax valga) and significant soft tissue contractures, muscle imbalance, and muscular weakness make THA a challenging surgical procedure in this patient population, and can predispose to dislocation and poor functional outcome following surgery. THA can, however, result in substantial pain relief and functional improvement, and can be safely performed, provided certain technical considerations are addressed. The patient's motor strength and functional status (ambulatory vs. “sitter”) should be carefully assessed preoperatively, since both of these factors may affect the choice of surgical approach and component position. Significant soft tissue contractures should be released at the time of surgery. Although these can be frequently performed “open”, percutaneous adductor tenotomy is occasionally necessary for patients with significant adduction contractures. Patients requiring significant soft tissue releases may benefit from 6 weeks of bracing to allow soft tissues to heal in appropriately and minimise risk of dislocation during this period of time. Use of modular femoral components that allow for correction of excessive femoral anteversion, should be considered in patients with coexistent dysplasia and neuromuscular disease (i.e., CP or polio). Large femoral head components should also be considered in patients with increased risk factors for dislocation. Despite their obvious theoretical advantages, the use of large head metal on metal THAs should be used with extreme caution in view of growing concerns about these devices. Although constrained acetabular liners are associated with an increased risk of mechanical failure, their use should be strongly considered in patients with significant motor weakness or major soft tissue deficiencies. Meticulous soft tissue closure of the capsule of the hip is recommended, especially when performing THA through a posterior approach. Patients with neuromuscular disorders associated with spasticity and involuntary movements need to be optimally treated medically prior to and indefinitely after THA. There are limited reports of outcomes following THA in patients with neuromuscular disorders, however, some generalizations based on underlying diagnosis can be made. Patients with cerebral palsy and polio frequently have acetabular dysplasia, excessive femoral anteversion and LLD, and although durability does not seem to be a major concern, dislocation and instability is relatively common and needs to be addressed. Durability and instability do not appear to be major concerns in patients with Parkinson's disease, however, these patients have frequent medical complications perioperatively and have deterioration in function over time due to the progressive nature of their underlying disorder. Patients with previous CVA also appear to have acceptable durability and dislocation risk, but are at high risk of developing heterotopic ossification postoperatively. Patients with Charcot arthropathy or myelodysplasia are at high risk of instability and appear to have limited functional improvement following THA. As a result, the consensus of opinion is that THA is contraindicated in these patients

We report catastrophic early failure of a cemented total hip replacement comprising a modular femoral component with a Zirconia ceramic head and an acetabular component of cross-linked ultra-high molecular-weight polyethylene (Hylamer). Between 1995 and 1999 we implanted 29 hips in 26 patients with a mean age of 49.2 years. Survivorship analysis in this group revealed a failure rate of 67.6% at five years. All hips which failed did so because of aseptic loosening with progressive osteolysis or radiolucencies. We therefore recommend early and regular review of all patients with this combination of implants and early revision surgery in order to avoid massive bone loss