Hip capsule biomechanics after arthroplasty: the effect of implant, approach, and surgical repair.

AIMS: The hip's capsular ligaments passively restrain extreme range of movement (ROM) by wrapping around the native femoral head/neck. We determined the effect of hip resurfacing arthroplasty (HRA), dual-mobility total hip arthroplasty (DM-THA), conventional THA, and surgical approach on ligament function. MATERIALS AND METHODS: Eight paired cadaveric hip joints were skeletonized but retained the hip capsule. Capsular ROM restraint during controlled internal rotation (IR) and external rotation (ER) was measured before and after HRA, DM-THA, and conventional THA, with a posterior (right hips) and anterior capsulotomy (left hips). RESULTS: Hip resurfacing provided a near-native ROM with between 5° to 17° increase in IR/ER ROM compared with the native hip for the different positions tested, which was a 9% to 33% increase. DM-THA generated a 9° to 61° (18% to 121%) increase in ROM. Conventional THA generated a 52° to 100° (94% to 199%) increase in ROM. Thus, for conventional THA, the capsule function that exerts a limit on ROM is lost. It is restored to some extent by DM-THA, and almost fully restored by hip resurfacing. In positions of low flexion/extension, the posterior capsulotomy provided more normal function than the anterior, possibly because the capsule was shortened during posterior repair. However, in deep flexion positions, the anterior capsulotomy functioned better. CONCLUSION: Native head-size and capsular repair preserves capsular function after arthroplasty. The anterior and posterior approach differentially affect postoperative biomechanical function of the capsular ligaments. Cite this article: Bone Joint J 2019;101-B:426-434.

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.

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.

Optimizing for head height, head offset, and canal fit in a set of uncemented stemmed femoral components.

When inserting an uncemented hip stem, the objectives are to obtain a close fit of the stem in the canal and anatomic head placement. Our goals were to formulate a set of stems which would satisfy these two objectives, and to test the resulting templates on sequential radiographs of hip replacement patients. Using 98 cases for which a custom primary hip had been designed, thirteen dimensional parameters for a hip stem were defined, most importantly proximal medial width (PMW), proximal lateral width (PLW), head offset (HOF), head height (HHT), mid-stem diameter (BD), and distal diameter (DD). These parameters were analyzed in 155 patients' radiographs, and the resulting data were evaluated to obtain the optimal combinations of parameters. A 14-size stem system was defined and evaluated on the AP radiographs of 103 successive hip replacement patients. For each stem diameter between 11 and 17 mm, two pairs of PMW and PLW values, equivalent to 'varus' and 'valgus' shapes, provided the best fit for the population of radiographs. The template analysis showed that out of 103 cases, 93% of offsets were within 4mm of ideal, while 81% of heights were within 1mm of ideal, and 99% were within 4mm of the ideal. Canal fit was within 1.5mm in the proximal-medial Gruen Zone 7 in 58% of the cases. The dimensional parameters of the 14 size system enabled the close matching of the important dimensional parameters simultaneously. The error that did occur could largely be corrected by modular heads and by minor canal broaching. By providing two stem shape variations for each stem diameter, our system achieved an accurate head center position while simultaneously obtaining a sufficiently close fit in the canal.

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.

Design and application of combined hip-knee intramedullary joint replacements.

Cases in which there is a total hip arthroplasty and a stemmed total knee arthroplasty in the same femur, with loosening of 1 or both components, with serious endosteal bone loss or even a fracture between the stems present a difficult reconstruction problem. We describe a reconstruction using a combined hip and stemmed knee, designed so that they could be rigidly connected during the surgical procedure. The advantages of this implant design are that the entire femur with its muscle attachments is preserved, and the inherent stability allows for immediate weight bearing. To determine the viability of the connection between the hip and the knee, a stress analysis was carried out using finite element analysis. Guidelines were thus provided for the required metal and cement thicknesses. Three case examples are presented with an average follow-up of 3 years. It was shown that the combined hip-knee implant could provide successful results for these difficult reconstructive problems in appropriately selected cases.

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.