Muthu Ganapathi

Heterotopic Ossification After Surface Replacement Arthroplasty and Total Hip Arthroplasty: A Randomized Study

With a randomized clinical trial, we compared the incidence and severity of heterotopic ossification in cohorts of patients who have undergone either surface replacement arthroplasty or total hip arthroplasty at a minimum follow-up of 1 year. Surface replacement arthroplasty group had a significantly higher rate of severe heterotopic ossification (Brooker grades 3-4) than the total hip arthroplasty group, 12.6% (13/103) vs 2.1% (2/97) respectively (P = .02). Grade 4 heterotopic ossification was observed (4.9%, 5/103) exclusively in the surface replacement arthroplasty group. Patients with severe heterotopic ossification had significantly inferior functional outcome scores. Surgeons offering surface replacement must be aware of this risk and use meticulous surgical technique and consider routine prophylaxis against heterotopic ossification.

Range of motion of large head total hip arthroplasty is greater than 28 mm total hip arthroplasty or hip resurfacing.

BACKGROUND Reduced range of motion of the hip has a detrimental influence on lower limb function. Large diameter head total hip arthroplasty may theoretically have a greater potential for restoring normal hip range of motion due to greater head-neck diameter ratio, and hence provide better function compared to conventional or hip resurfacing arthroplasty. METHOD At minimum one year follow-up, range of motion of the operated and contra lateral hips was clinically assessed using digital photographs and bony landmarks in a clinical comparative study. We assessed if 1) large diameter head total hip arthroplasty (55 patients) restores better hip range of motion compared to 28 mm total hip arthroplasty (50 patients) or hip resurfacing (60 patients) 2) large diameter head total hip arthroplasty achieves same hip range of motion as contra lateral normal hips and 3) hip range of motion correlates with the WOMAC score. FINDINGS The large diameter head total hip arthroplasty group had significantly greater total arcs of motion (approximately 20°), mostly due to an increase of hip flexion and external rotation, but did not reach normal hip motion. The hip range of motion showed significant correlation with the WOMAC score, especially the flexion arc. INTERPRETATION The better hip range of motion of large diameter head total hip arthroplasty is likely due to the greater head to neck diameter ratio and hence seems to be the best option to optimize range of hip motion and improve function after hip arthroplasty.

Residual groin pain at a minimum of two years after metal-on-metal THA with a twenty-eight-millimeter femoral head, THA with a large-diameter femoral head, and hip resurfacing.

BACKGROUND Groin pain may persist in up to 4.3% of patients after total hip arthroplasty and up to 18% of patients one year after hip resurfacing. The incidence of this problem after total hip arthroplasty with a large-diameter femoral head is unknown. METHODS We analyzed the natural history of groin pain and its clinical consequences during the first two years after three types of hip arthroplasty. Data were collected prospectively on 279 patients. Eighty-five patients had a polyethylene sandwich metal-on-metal total hip arthroplasty with a 28-mm-diameter femoral head, 105 had hip resurfacing, and eighty-nine had a total hip arthroplasty with a large-diameter femoral head component with three other cup designs (forty-nine in this group had the same monoblock acetabular cup design as those who had hip resurfacing). RESULTS At the twenty-four-month follow-up evaluation, seventy-seven patients (28%) reported at least one painful area around the hip and thirty-four patients (12.2%) had pain at more than one location. At three months, the incidence of groin discomfort was significantly increased in those who had hip resurfacing (30.5%) and in those who had total hip arthroplasty with a large-diameter femoral head (30%) compared with those who had total hip arthroplasty with a 28-mm femoral head (18.3%). This incidence decreased at two years (14.9%, 16.9%, and 12.9%, respectively). At twenty-four months postoperatively, eleven (four who had hip resurfacing, six who had total hip arthroplasty with the large-diameter head, and one who had total hip arthroplasty with the 28-mm head) of forty-one patients who had groin pain had not reported groin pain at previous follow-up evaluations. Of the forty-one patients reporting groin pain at the time of the last follow-up, twenty-three patients (56%) did not seek further evaluation or treatment, nine had revision surgery (22%), and the remaining nine patients thought the pain was substantial enough to warrant further evaluation and treatment. CONCLUSIONS When the exact source of groin pain cannot be found after total hip arthroplasty, careful follow-up should be done as local reactions to metal-on-metal implants and component loosening may take time to become apparent clinically or on imaging studies.

Blood and urine metal ion levels in young and active patients after Birmingham hip resurfacing arthroplasty

This is a longitudinal study of the daily urinary output and the concentrations in whole blood of cobalt and chromium in patients with metal-on-metal resurfacings over a period of four years.Twelve-hour urine collections and whole blood specimens were collected before and periodically after a Birmingham hip resurfacing in 26 patients. All ion analyses were carried out using a high-resolution inductively-coupled plasma mass spectrometer. Clinical and radiological assessment, hip function scoring and activity level assessment revealed excellent hip function.There was a significant early increase in urinary metal output, reaching a peak at six months for cobalt and one year for chromium post-operatively. There was thereafter a steady decrease in the median urinary output of cobalt over the following three years, although the differences are not statistically significant. The mean whole blood levels of cobalt and chromium also showed a significant increase between the pre-operative and one-year post-operative...

Postural Balance During Quiet Standing in Patients With Total Hip Arthroplasty With Large Diameter Femoral Head and Surface Replacement Arthroplasty

OBJECTIVE To compare postural balance between patients who have had either a large diameter head total hip arthroplasty or surface replacement arthroplasty. DESIGN Observational study. SETTING Outpatient biomechanical laboratory. PARTICIPANTS Two groups of 14 patients with surface replacement or large diameter head total hip arthroplasties recruited from a larger randomized study and 14 control subjects. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Postural balance during quiet standing in dual and one-leg stance (operated leg), hip abductor muscle strength, clinical outcomes, and radiographic analyses were compared between groups. RESULTS Compared to the control group, patients in both groups showed smaller center of pressure displacement amplitude in the medial-lateral direction in dual stance. Patients with large diameter head total hip arthroplasty showed lower hip abductor muscle strength compared to control subjects. There was statistical difference between the 2 patient groups in biomechanical reconstruction of the hip. Despite these differences, there was no significant difference in the ability to complete the one-leg stance task between the 3 groups. CONCLUSIONS The muscular strength in the operated limb could be mainly responsible for the lower center of pressure displacement amplitude compared to control subjects. However, the ability to complete the one-leg stance demonstrates that patients do not fear to load the hip prosthesis when needed. The large diameter femoral head may be a major mechanical factor contributing to these results.

Factors affecting acetabular bone loss during primary hip arthroplasty – A quantitative analysis using computer simulation

BACKGROUND Although, various factors may affect the degree of acetabular bone loss during primary hip arthroplasty, they have not been quantified previously. METHODS We assessed the influence of using various reamer diameters, designs and reaming depth on the amount of bone removed during acetabular preparation by simulated reaming in a three-dimensional pelvic model, using computer software. FINDINGS The least amount of bone loss (6185 mm3) providing optimal bone contact with the acetabular articular surface occurred with a 165 degrees reamer design. Increase in reamer diameter, reaming depth and subtending angle of the reamer resulted in disproportionately large increase in the amount of bone resected compared to the relatively small increase in the reamer-bone contact area. INTERPRETATION Surgeons must be aware of the relative influence of the reaming technique and the implant design on the amount of acetabular bone resection to optimize acetabular bone preservation during primary hip arthroplasty.

Randomised controlled trial comparing two methods of acetabular cup positioning during total hip arthroplasty.

BACKGROUND Acetabular cup positioning is an important technical aspect in total hip arthroplasty. Most surgeons estimate cup abduction angle during surgery with the insertion rod position according to the patients body anatomical landmarks or other reference points in the operating room. High acetabular component abduction angle is associated with an increased risk of dislocation, premature polyethylene wear and osteolysis. METHOD To evaluate the potential benefits of a new technique for vertical acetabular cup positioning, 100 acetabular cups were randomised to be inserted with or without an inclinometer. Abduction angles were measured on postoperative radiographs by 2 evaluators blind to the treatment group. RESULTS Of the cups, 57% (27/47) were positioned within the desirable abduction angle range of 40-49 with the inclinometer, compared with 50% (27/53) by visuospatial perception (p=0.454). The proportion of cups positioned outside a safe angle range of 30-55 was low in both groups: 6% (3/47) for the inclinometer group versus 4% (2/53) for the visuospatial perception group (p=0.536). CONCLUSION The use of an inclinometer did not significantly improve the acetabular cup abduction angle obtained by our group of surgeons when compared with visuospatial perception. Newer techniques such as navigation may be useful in further optimising cup positioning and reducing the outliers.

Reply to Letter to Editor: Femoral Component Positioning in Hip Resurfacing with and Without Navigation

We acknowledge Dr. Andrea Emilio Salvi for his general comments and opinions on hip resurfacing surgical technique and factors that may affect clinical outcome. Even if no specific question or comment is directly related to our study [2], we will try to provide a scientific input on the points raised.