The influence of spine-hip relations on total hip replacement: A systematic review.

Sagittal pelvic kinematics along with spino-pelvic angular parameters have recently been studied by numerous investigators for their effect on total hip replacement (THR) clinical outcomes, but many issue of spine-hip relations (SHR) are currently unexplored. Therefore, our review aims at clarifying the following questions: is there any evidence of a relationship between articular impingement/dislocation risk in primary THR and (1) certain sagittal pelvic kinematics patterns, (2) pelvic incidence, and (3) types of SHRs? A systematic review of the existing literature utilising PubMed and Google search engines was performed in January 2017. Only clinical or computational studies published in peer-reviewed journals over the last five years in either English or French were reviewed. We identified 769 reports, of which 12 met our eligibility criteria. A review of literature shows that sagittal pelvic kinematics, but not the pelvic incidence, influences the risk of prosthetic impingement/dislocation. We found no study having assessed the relationship between this risk and the types of SHRs. Sagittal pelvic kinematics is highly variable among individuals and certain kinematic patterns substantially influences the risk of prosthetic impingement/dislocation. Recommendations for cup positioning are therefore switching from a systematic to a patient-specific approach, with the standing cup orientation Lewinneck safe zone progressively giving way to a new parameter of interest: the functional orientation of the cup. Based on a recently published classification for SHRs, We propose a new concept of "kinematically aligned THR" for the purposes of THR planning. Further studies are needed to investigate the relevance of such a classification towards the assumptions and hypothesis we have made. Level of evidence,- Level IV, systematic review of level III and IV studies.

Spine-hip relations add understandings to the pathophysiology of femoro-acetabular impingement: A systematic review.

Relationship between hip pathoanatomy and symptomatic FAI has been reported to be weak. This is explained by the reciprocal interaction between proximal femur and acetabular anatomies, but potentially also by the individual spine-hip relations (SHR). The key-answer for a complete understanding of the pathophysiology of FAI might lie in the comprehension of the SHRs, which have not yet been fully addressed. Therefore we conducted a systematic review to answer the subsequent questions: Is there any evidence of a relationship between FAI and (1) sagittal pelvic kinematics, (2) pelvic incidence, and (3) types of SHRs? A systematic review of the existing literature utilizing PubMed and Google search engines was performed in December 2016. Only studies published in peer-reviewed journals over the last ten years in either English or French were reviewed. We identified 90 reports, of which 9 met our eligibility criteria. Review of literature shows Caucasian FAI patients have a pelvis with higher anterior tilt, lesser sagittal mobility, and lower pelvic incidence compared to healthy patients. We found no study having assessed the relationship between SHR and FAI. In order to help further investigations at answering questions 3 and 4, we have developed a classification for SHRs. The classification according spino-pelvic parameters allows identifying patient at risk regarding FAI occurrence. Higher anterior pelvic tilt in standing, sitting and squatting positions and lower pelvic incidence have been found to correlate with symptomatic FAI. Because defining the individual SHR might increase the understanding of the pathophysiology of hip impingement, we have developed a classification for SHRs. LEVEL OF EVIDENCE: Level IV, systematic review of Level III and IV studies.

Return to sporting activity after Birmingham hip resurfacing arthroplasty: Mid term results.

BACKGROUND: Hip resurfacing arthroplasty (HRA) is primarily indicated for young, active patients with disabling coxarthrosis who wish to remain active and return to sports after surgery. Relatively few prospective studies have assessed return to sporting activity and impact of gender and age on this. MATERIALS AND METHODS: Seventy-nine consecutive patients treated with HRA were included. Patients were reviewed clinically and radiologically. Function was assessed using the modified University of California Los Angeles (UCLA) activity score. The Oxford, Harris and WOMAC hip scores were calculated. RESULTS: Average age at the time of surgery was 54.9 years (range 34.5-73.6 years). Average preoperative and postoperative UCLA scores were 4 and 7.6 respectively. Patients were involved in 2 (0-4) sporting activities preoperatively and 2 (0-5) postoperatively. Preoperative and postoperative Oxford Hip Scores, Harris Hip Score and WOMAC scores were 40, 46 and 51 and 16, 94 and 3 respectively (P < 0.0001). Patients returned to sports at an average of 3 months postoperatively. CONCLUSION: Patients were able to return to sports by 3 months and perform the same number of activities at preoperative intensity. Activity levels are maintained up to the medium term with few complications.

Which factors determine the wear rate of large-diameter metal-on-metal hip replacements? Multivariate analysis of two hundred and seventy-six components.

BACKGROUND: Determining the relationship between clinical factors and engineering analysis of retrieved hip implants can help our understanding of the mechanism of device failure. This is particularly important for metal-on-metal hip arthroplasties because the most common cause of failure is unexplained. We sought to understand the variation in wear rates in a large series of retrieved metal-on-metal hip arthroplasty components. METHODS: We prospectively recorded preoperative, intraoperative, and postoperative data to study the effect on both head and cup wear rates of the following variables: patient sex, cause of failure, manufacturer type, resurfacing or modular design, blood cobalt and chromium levels, edge-loading, femoral head size, and cup inclination angle. We analyzed 276 components (138 femoral head and acetabular cup couples) retrieved from failed metal-on-metal hip replacements. RESULTS: We found a high rate of edge-loading (64%), but only forty-three (31%) of 138 hips had a cup inclination angle of >55°. Multivariate analysis showed that the most important factor responsible for the variation in wear rate was the presence or absence of edge-loading, even when adjusted for cup inclination angle. Strong positive correlations were found between acetabular cup and femoral head wear rates and between wear rates and both blood cobalt and chromium ion levels. CONCLUSIONS: Multivariate analysis of nine factors found that edge-loading was the most important predictor of wear rate and occurred in two-thirds of failed metal-on-metal hip replacements. The majority did not have excessive cup inclination angles: 68% had an inclination angle of ≤55°. This finding, together with the relatively low median wear rate of the components in our study, suggests that cup position and/or wear rate may not be the only outcome related to failure of metal-on-metal hip replacements.

Uncemented computer-assisted design-computer-assisted manufacture femoral components in revision total hip replacement: a minimum follow-up of ten years.

We prospectively evaluated the long-term outcome of 158 consecutive patients who underwent revision total hip replacement using uncemented computer-assisted design-computer-assisted manufacture femoral components. There were 97 men and 61 women. Their mean age was 63.1 years (34.6 to 85.9). The mean follow-up was 10.8 years (10 to 12). The mean Oxford, Harris and Western Ontario and McMaster hip scores improved from 41.1, 44.2 and 52.4 pre-operatively to 18.2, 89.3 and 12.3, respectively (p < 0.0001, for each). Six patients required further surgery. The overall survival of the femoral component was 97% (95% confidence interval 94.5 to 99.7). These results are comparable to those of previously published reports for revision total hip replacement using either cemented or uncemented components.

Uncemented custom computer-assisted design and manufacture of hydroxyapatite-coated femoral components: survival at 10 to 17 years.

We present the 10- to 17-year results of 112 computer-assisted design computer-assisted manufacture femoral components. The total hip replacements were performed between 1992 and 1998 in 111 patients, comprising 53 men and 58 women. Their mean age was 46.2 years (24.6 to 62.2) with a mean follow-up of 13 years (10 to 17). The mean Harris Hip Score improved from 42.4 (7 to 99) to 90.3 (38 to 100), the mean Oxford Hip Score from 43.1 (12 to 59) to 18.2 (12 to 51) and the mean Western Ontario MacMasters University Osteoarthritis Index score from 57.0 (7 to 96) to 11.9 (0 to 85). There was one revision due to failure of the acetabular component but no failures of the femoral component. There were no revisions for aseptic loosening. The worst-case survival in this cohort of custom femoral components at 13.2 years follow-up was 98.2% (95% confidence interval 95 to 99). Overall survival of this series of total hip replacements was 97.3% (95% confidence interval 95 to 99). These results are comparable with the best medium- to long-term results for femoral components used in primary total hip replacement with any means of fixation.

Circulating levels of cobalt and chromium from metal-on-metal hip replacement are associated with CD8+ T-cell lymphopenia.

We carried out a cross-sectional study with analysis of the demographic, clinical and laboratory characteristics of patients with metal-on-metal hip resurfacing, ceramic-on-ceramic and metal-on-polyethylene hip replacements. Our aim was to evaluate the relationship between metal-on-metal replacements, the levels of cobalt and chromium ions in whole blood and the absolute numbers of circulating lymphocytes. We recruited 164 patients (101 men and 63 women) with hip replacements, 106 with metal-on-metal hips and 58 with non-metal-on-metal hips, aged < 65 years, with a pre-operative diagnosis of osteoarthritis and no pre-existing immunological disorders. Laboratory-defined T-cell lymphopenia was present in 13 patients (15%) (CD8(+) lymphopenia) and 11 patients (13%) (CD3(+) lymphopenia) with unilateral metal-on-metal hips. There were significant differences in the absolute CD8(+) lymphocyte subset counts for the metal-on-metal groups compared with each control group (p-values ranging between 0.024 and 0.046). Statistical modelling with analysis of covariance using age, gender, type of hip replacement, smoking and circulating metal ion levels, showed that circulating levels of metal ions, especially cobalt, explained the variation in absolute lymphocyte counts for almost all lymphocyte subsets.

A displaced acetabular component causing femoral neck notching following hip resurfacing.

We describe the case of a patient who developed a notch on the femoral neck following a hip resurfacing operation as a result of a displaced acetabular component. The acetabular cup displaced in the coronal plane and impinged on the femoral neck leading to a large notch in the inferior femoral neck.

Revision of the Birmingham Hip Resurfacing cup: technical notes and the use of a novel technique to overcome unique problems.

The number of hip resurfacing procedures performed in the United Kingdom has doubled in the last four years reflecting its popularity among orthopaedic surgeons. Of the available options the Birmingham Hip Resurfacing (BHR) prosthesis has been the most popular choice in this country. Despite this revision rates have been shown to be higher in the resurfacing group compared to the total hip arthroplasty group particularly in the early postoperative period. Revision of the BHR acetabular component is technically demanding due to several unique design features of this component. We discuss these features and describe a novel reliable and reproducible technique for revision of the BHR cup.

Does Chiari osteotomy compromise subsequent total hip arthroplasty?

We compared 28 total hip arthroplasties done in dysplastic hips after previous Chiari osteotomy (group I) with a well-matched control group of 50 primary procedures (group II) done during the same period at an average follow-up of 5 years (range, 25-199 months). Group I required significantly less acetabular augmentation, had significantly shorter operative times, had less intraoperative blood loss, and had fewer complications than group II. There was no significant difference between the 2 groups in terms of clinical or radiographic outcome. Total hip arthroplasty after a successful Chiari osteotomy leads to medium-term results similar to those of other dysplastic hips. In our experience, less bone grafting was required, better coverage of the cup by host-bone was obtained, and the center of motion of the hip was more anatomic. Chiari osteotomy may delay the need for total hip arthroplasty, may facilitate acetabular reconstruction, and does not seem to compromise the medium-term clinical or radiographic outcome.

Two-stage uncemented revision hip arthroplasty for infection.

We treated 50 consecutive patients with infected total hip arthroplasties according to a standard protocol. Previous surgery to eradicate the infection had been attempted in 13 patients and discharging sinuses were present in 20. Aspiration arthrography was routinely carried out before our interventions. The first stage was a meticulous removal of all foreign and potentially infected material. Samples were taken for culture and a thorough lavage carried out. Antibiotic-loaded beads were placed in the femoral shaft and an antibiotic-loaded cement ball in the acetabulum. At the second stage an uncemented arthroplasty was introduced. Bone allograft was used in 18 patients. The interval between procedures was usually three weeks, but this was extended if the wound was slow to heal or there was extensive bony destruction. Appropriate antibiotics were given for three months. At a mean follow-up of 5.8 years the rate of reinfection was 8% (4 patients). Two of these patients have had another, successful, two-stage revision. At this medium-term review, a satisfactory clinical and radiological outcome was obtained in all except two patients.

Stability and bone preservation in custom designed revision hip stems.

Three types of uncemented femoral stems were designed for patients having revision hip surgery, with the goals of promoting axial stability and preserving proximal bone stock. These stems were made individually using computer design and manufacturing technology. Various design features were examined using nonlinear finite element analysis. All stems had lateral, medial, and anterior flares in the proximal region, proximal hydroxyapatite coating, and a collar. Based on a published classification system, the three designs were found suitable for variously encountered cavitary defects. For cases involving small amounts of bone destruction, a primary type of stem was used. With severe cases, an extended polished stem was used. For the worst cases, an extended stem with longitudinal cutting flutes and complete hydroxyapatite coating was necessary. The axial migration was measured radiographically for a 2-year period. The migration rates were comparable with those seen in cemented primary and in custom primary hydroxyapatite coated stems. Dual energy x-ray absorptiometry data were obtained during a 4-year postoperative period. Average bone density in all regions was maintained within 12% of the immediate postoperative values. It was concluded that the proposed system for treating patients needing revision hip surgery showed desirable properties that were comparable to primary hip replacements.

Uncemented total hip arthroplasty with subtrochanteric derotational osteotomy for severe femoral anteversion.

Total hip joint arthroplasty (THA) in the presence of severe femoral anteversion (>50 degrees) is technically demanding. This problem is often encountered in patients with osteoarthritis secondary to hip joint dysplasia or congenital dislocation. We describe a method of THA in which an uncemented femoral prosthesis is used in conjunction with subtrochanteric derotational osteotomy. This technique allows the restoration of the normal proximal femoral anatomy, including the abductor muscle lever arm without resorting to greater trochanteric transfer. Correction of the excessive femoral anteversion avoids the tendency for postoperative anterior instability. The osteotomy site may also serve as the site for femoral shortening or angular correction when required, which preserves the normal femoral flare. The prostheses used were custom CAD/CAM (computer-assisted design/computer-assisted manufacturer) in design and had the following features: a close intramedullary proximal fit, with collar, lateral flare, and hydroxyapatite coating to achieve early proximal fixation, and longitudinally cutting fluted stem to provide immediate rotational stability across the osteotomy site. Although we used CAD/CAM custom prostheses, off-the-shelf uncemented hip prostheses with similar design features have become available. We report on 7 patients who underwent THA using this technique. The average patient age was 49 years (range, 34-61 years) with a mean follow-up period of 31 months (range, 16-60 months). To date, all cases have had a satisfactory outcome with evidence of union at the osteotomy site. Harris hip scores improved from an average of 44 preoperatively to 91 by the end of follow-up period. One case was complicated by delayed union at the osteotomy site, which was successfully corrected with bone grafting and temporary plate stabilization.

Acetabular reconstruction with morcellized allograft and ring support: a medium-term review.

Acetabular bone stock deficiency is commonly encountered in revision hip surgery. A number of techniques are available to address this problem, including the use of particulate allograft with reconstruction rings in an effort to provide a stable construct and replenish bone stock. Our technique and results using such devices in complex acetabular deficiencies are described. In the setting of a large nmedial segmental or cavitary acetabular defect, morcellized bone-graft is used to reconstitute the acetabular floor. This graft is reverse reamed until its depth allows screw fixation of a metallic support ring. The screws also serve to compress the graft. A polyethylene acetabular component is then cemented into the reconstituted acetabulum with full freedom of orientation. A series of 48 patients in whom this technique was employed is presented. These cases have been clinically and radiologically reviewed with a mean follow-up of 64 months (range, 25-102 months). Good bony incorporation with stable acetabular components was seen in all but the two cases in which sepsis predominated.