Introduction

As population grows older, and patients receive primary joint replacements at younger age, more and more patients receive a total hip prosthesis nowadays. Ten-year failure rates of revision hip replacements are estimated at 25.6%. The acetabular component is involved in over 58% of those failures. From the second revision on, the pelvic bone stock is significantly reduced and any standard device proves inadequate in the long term [Villanueva et al. 2008]. To deal with these challenges, a custom approach could prove valuable [Deboer et al. 2007].

Introduction. Acetabular revision surgery is challenging due to severe bone defects. Burch-Schneider anti-protrusion cages (BS cage: Zimmer-Biomet) is one of the options for acetabular revision, however higher dislocation rate was reported. A computed tomography (CT)-based navigation system indicates us the planned direction for implantation of a cemented acetabular cup during surgery. A large diameter femoral head is also expected to reduce the dislocation rate. The purpose of this study is to investigate short-term results of BS cage in acetabular revision surgery combined with the CT-based navigation system and the use of large diameter femoral head. Methods. Sixteen hips of fifteen patients who underwent revision THA using allografts and BS cage between September 2013 and December 2017 were included in this study with the follow-up of 2.7 (0.1–5.0) years. There were 12 women and three men with a mean age of 78.6 years (range, 59–61 years). The cause of acetabular revision was aseptic loosening in all hips. The failed acetabular cup was carefully removed, and acetabular bone defect was graded using the Paprosky classification. Structural allografts were morselized and packed for all medial or contained defects. In some cases, solid allograft was implanted for segmental defects. BS cage was molded to optimize stability and congruity to the acetabulum and fixed with 6.5 mm titanium screws to the iliac bone. The inferior flange was slotted into the ischium. The upside-down trial cup was attached to a straight handle cup positioner with instrumental tracker (Figure 1) and placed on the rim of the BS cage to confirm the direction of the target angle for cement cup implantation under the CT-based navigation system (Stryker). After removing the cement spacer around the X3 RimFit cup (Stryker) onto the BS cage for available maximum large femoral head, the cement cup was implanted with confirming the direction of targeting angle. Japanese Orthopedic Association score (JOA score) of the hip was used for clinical assessment. Implant position, loosening, and consolidation of allograft were assessed using anterior and lateral radiographies of the pelvis. Results. Fifteen hips had a Paprosky IIIB defect, and one hip had a pelvic discontinuity. JOA score significantly improved postoperatively. No radiolucent lines and no displacement of BS cage could be found in 9 of 15 hips. Consolidation of allografts above the protrusion cage was observed in these patients. Displacement of BS cage (>5mm) was observed in 6 hips and displacement was stopped with allograft consolidation in 5 of 6 hips. The other patient showed lateral displacement of BS cage and underwent revision surgery. Average cup inclination and anteversion angles were 37.7±5.0 degree and 24.6±7.2 degree, respectively. 12 of 16 patients were included in Lewinnek's safe zone. One patient with 32 mm diameter of the femoral head had dislocation at 17 days postoperatively. All patients who received ≥36mm diameter of femoral head showed no dislocation. Conclusions. CT-based navigation system and the use of large femoral head may influence the prevention of dislocation in the acetabular revision surgery with BS cage for severe acetabular bone defects

Introduction. Modular tapered implants have been suggested as the optimal treatment in patients with severe femoral bone loss undergoing revision total hip arthroplasty (THA). The purpose of this study is to describe minimum 2 year follow up of patients treated with modular tapered prostheses for Paprosky type IIIB and IV femoral bone loss in revision THA. Methods. 44 Consecutive patients with Paprosky type IIIB (23) or IV (21) femurs undergoing revision total hip arthroplasty to cementless modular tapered prostheses were studied. Harris Hip Scores were obtained prior to revision on all patients except those presenting with acute implant failure or periprosthetic fracture. 10 Patients were deceased within 2 years of surgery; the remaining 18 were followed for an average of 42 months (range 25-69 months). Clinical outcomes were measured using the Harris Hip Score, and radiographs were assessed for signs of stem loosening or subsidence >4mm. Results. No further revisions were required in patients who were deceased within 2 years. In those with >2 year follow up, there were 4 additional revisions: 1 for infection, 2 for instability, and 1 for periprosthetic fracture. In patients with surviving implants, the mean Harris Hip Score improved from 33 (range 11-49) pre-operatively to 77 (range 55-100), and there was no radiographic evidence of loosening or subsidence at time of final follow up. Conclusions. These outcomes support the use of modular tapered implants as a safe and effective option for revision arthroplasty of type IIIB and IV femurs

Purpose:. Acetabular bone loss during revision total hip arthroplasty (THA) poses a challenge for reconstruction as segmental and extensive cavitary defects require structural support to achieve prosthesis stability. Trabecular metal (TM) acetabular augments structurally support hemispherical cups. Positive short-term results have been encouraging, but mid- to long-term results are largely unknown. The purpose of this study was to determine the continued efficacy of TM augments in THA revisions with significant pelvic bone loss. Methods:. Radiographs and medical records of 51 patients who had undergone THA revision with the use of a TM augment were retrospectively reviewed. Acetabular defects were graded according to the Paprosky classification of acetabular deficiencies based on preoperative radiographs and operative findings. Loosening was defined radiographically as a gross change in cup position, change in the abduction angle (>5°), or change in the vertical position of the acetabular component (>8 mm) between initial postoperative and most recent follow-up radiographs (Figure 1). Results:. Eleven patients had incomplete radiographic follow-up and were excluded. The study population included 17 men and 23 women, averaging 68.1 ± 14.1 years of age (range, 37–91), with average radiographic follow-up of 19.0 months (range, 2.4–97.4). Reasons for revision included osteolysis (n = 20, 38.5%), component loosening (n = 18, 15.4%), and periprosthetic fracture (n = 6, 11.5%). All patients underwent revision THA using a TM multi-hole revision acetabular cup and TM acetabular augment(s) to fill bony defects. Morcellized allograft was used in 9 patients. There were 33 Paprosky Type IIIA and seven Paprosky Type IIIB defects. One patient with Paprosky Type IIIB had catastrophic failure of the reconstructive construct three months postoperatively. The remaining 39 acetabular revisions demonstrated signs of bony ingrowth at the latest follow-up. There were no radiolucent lines suggestive of loosening, and no significant differences in abduction angle (p = 0.78), vertical distance between the superolateral edge of the cup and the trans-ischial reference line (p = 0.96), or the vertical distance between the center of the femoral head and trans-ischial reference line (p = 0.75) between the initial postoperative and most recent follow-up radiographs (Figure 2). Discussion and Conclusion:. Achieving fixation and long-term stability in THA revisions with segmental and/or cavitary bone loss is challenging. TM augments provide a modular structural system to achieve bony ingrowth, while avoiding large structural allografts, cages, and custom implants. At latest follow-up, 39 revision hips remained well-fixed with no evidence of loosening. One patient with a significant surgical history of infection, periprosthetic femur fracture, and 2 prior revision surgeries before acetabular reconstruction had an early clinical failure. Trabecular metal augments can be used for reconstruction of acetabular bone loss with good mid-term results. Continued follow-up is warranted for radiographic evaluation of bony integration and implant stability to determine long-term survivorship of these implants

Introduction:. Jumbo cups (58 mm or larger diameter in females and 62 mm or larger diameter in males), theoretically have lowered the percentage of bleeding bone that is required for osseointegration in severe acetabular defects. The purpose of this study was to analyze the safety and efficacy of Tritanium jumbo cups in patients with major acetabular defects (Paprosky type IIIa and IIIb) and assess the extent of osseointegration. Material and Methods:. From February 2007 and August 2010, 28 consecutive hips (26 patients, mean age of 69 years) underwent acetabular revision arthroplasty for treatment of Paprosky type IIIa and IIIb defects using Tritanium jumbo cups (Stryker, Mahwah, New Jersey). Results:. 14% of the hips had pelvic discontinuity. There was no intra-operative fracture. The initial stability was achieved in all hips, supplemented by screws. No Tantalum augments or bulk bone grafts were used in any of the cases. At mean follow-up of 4 years, there were no failures due to loosening or cup migration. Radiographic assessment showed osseointegration in all cups, ranging from 30% to 75% of the cup surface area as assessed in both anteroposterior and false profile views in Charnley zones I through VI. Discussion and conclusion:. In Paprosky type IIIb defect with pelvic discontinuity, jumbo cup can be used safely without the use of any augments. In pelvic dissociation, the fibrous tissue is stretched with jumbo cups in an under-reamed socket to achieve a fixation by distraction, especially in failed cemented sockets

Femoral revision in cemented THA might include some technical difficulties, based on the loss of bone stock and cement removal, which might lead to further loss of bone stock, inadequate fixation, cortical perforation or consequent fractures. Femoral impaction grafting, in combination with a primary cemented stem, allows for femoral bone restoration by incorporating and remodeling the allograft bone of the host skeleton. Historically, this was first performed and described in Exeter in 1987. Indications might include all femoral revisions with bone stock loss, while the Endo-Clinic experience is mainly based on revision of cemented stems. Nowadays our main indication is the Paprosky Type IIIb and Type IV. Contraindications are mainly: septical revisions, extensive circumferential cortical bone loss and noncompliance of the patient. Generally the technique creates a new endosteal surface to host the cemented stem by reconstruction of the cavitary defects with impacted morselised bone graft. This achieves primary stability and restoration of the bone stock. It has been shown, that fresh frozen allograft shows superior mechanical stability than freeze-dried allografts. Technical steps include: . –. removal of failed stem and all cement rests. –. reconstruction of segmental bone defects with metal mesh (containment). –. preparation of fresh frozen femoral head allografts with bone mill. –. optimal bone chip diameter 2 to 5 mm, larger chips for the calcar area (6–8 mm). –. insertion of an intramedullary plug including central wire, 2 cm distal the stem tip. –. introduction of bone chips from proximal to distal. –. impaction started by distal impactors over central wire, then progressive larger impactors proximal. –. insertion of a stem „dummy“ as proximal impactor and space filler. –. removal of central wire. –. retrograde insertion of bone cement (0.5 Gentamycin) with small nozzle syringe, including pressurisation. –. insertion of standard cemented stem. The cement mantle is of importance as it acts as the distributor of force between the stem and bone graft while sealing the stem. A cement mantle of at least 2 mm has shown favourable results. Post-operative care includes usually touch down weight bearing for 6–8 weeks, followed by 4–6 weeks of gradually increased weightbearing with a total of 12 weeks on crutches. Relevant complications include mainly femoral fractures due to the hardly impacted allograft bone. Subsidence of tapered polished implants might be related to coldflow within the cement mantle, however, it could also be related to micro cement mantle fractures, leading to early failure. Subsidence should be less than 5 mm. Survivorship with a defined endpoint as any femoral revision after 10-year follow-up has been reported by the Exeter group at over 90%. While survivorship for revision defined as aseptic loosening is even greater at above 98%. Within the last years various other authors and institutions reported similar excellent survivorships, above 90%. In addition a long-term follow-up by the Swedish arthroplasty registry in more than 1180 patients reported a cumulative survival rate of 94% after 15 years and 99% with the endpoint aseptic loosening. Impaction grafting is technically more challenging and more time consuming than cement free distal fixation techniques. However, it enables a reliable restoration of bone stock