Steven T. Woolson

Risk factors for dislocation during the first 3 months after primary total hip replacement

The prevalence of dislocation of a total hip replacement during the first 3 postoperative months was determined for a series of 315 patients who underwent a unilateral primary total hip operation. All operations were performed by 1 surgeon using a standardized posterior approach with a complete capsulectomy. All of the patients had a femoral component made by 1 manufacturer that had the same 28-mm modular head, the same femoral neck diameter, and the same offset for each size implant. One cementless acetabular component was used for all patients. All of the patients followed the same postoperative rehabilitation program. Of 315 patients, 14 sustained a dislocation, resulting in a prevalence of 4%. There were 13 posterior dislocations and 1 anterior dislocation. Because the surgeon, the surgical approach, the femoral component design, and the rehabilitation protocol were identical for all of these patients, the only variables that could affect the risk of dislocation were the size of the acetabular component and the femoral neck length, the type of fixation of the femoral component, the orientation of the acetabular component, and the characteristics of each patient. The patient characteristics that were studied included age; gender; height; weight; preoperative diagnosis; and a category termed cerebral dysfunction, which included a state of confusion during the hospital stay, a prior history of excessive alcohol consumption, or both of these conditions. Statistical analysis demonstrated 1 variable that was associated with a higher dislocation rate, the presence of cerebral dysfunction. There was a trend toward increased age as a risk factor. None of the other patient or component variables were found to be significant risk factors.

Cellular profile and cytokine production at prosthetic interfaces: STUDY OF TISSUES RETRIEVED FROM REVISED HIP AND KNEE REPLACEMENTS

The tissues surrounding 65 cemented and 36 cementless total joint replacements undergoing revision were characterised for cell types by immunohistochemistry and for cytokine expression by in situ hybridisation. We identified three distinct groups of revised implants: loose implants with ballooning radiological osteolysis, loose implants without osteolysis, and well-fixed implants. In the cemented series, osteolysis was associated with increased numbers of macrophages (p = 0.0006), T-lymphocyte subgroups (p = 0.03) and IL-1 (p = 0.02) and IL-6 (p = 0.0001) expression, and in the cementless series with increased numbers of T-lymphocyte subgroups (p = 0.005) and increased TNF alpha expression (p = 0.04). For cemented implants, the histological, histochemical and cytokine profiles of the interface correlated with the clinical and radiological grade of loosening and osteolysis. Our findings suggest that there are different biological mechanisms of loosening and osteolysis for cemented and cementless implants. T-lymphocyte modulation of macrophage function may be an important interaction at prosthetic interfaces.

Results of a method of leg-length equalization for patients undergoing primary total hip replacement

The postoperative leg-length discrepancy was determined radiographically for a consecutive series of 351 patients (408 hips) who underwent bilateral or unilateral primary total hip replacement using a single method of leg-length equalization by preoperative planning with overlay templates. The method of equalization was performed by a measurement of the femoral head and neck segment to be resected from a reference point at the superior aspect of the dislocated femoral head. The amount of femoral bone resected was determined preoperatively by determining the dimensions of the acetabular component thickness and the femoral component head and neck height that would be replacing this resected bone and adjusting this distance for any preexisting leg-length discrepancy. Using this leg-length equalization method, the length of the modular femoral head neck was chosen preoperatively, rather than using soft tissue tension across the prosthetic hip joint to determine whether the leg lengths were equal. Postoperative leg lengths were determined radiologically from a measurement from the acetabular teardrop to the lesser trochanter. Ninety-seven percent of the patients had a postoperative leg-length discrepancy that was less than 1 cm, and 86% had a leg-length difference that was 6 mm (1/4 inch) or less. The average postoperative discrepancy for these 351 patients was 1 mm.

Fixation, Polyethylene Wear, and Pelvic Osteolysis in Primary Total Hip Replacement

A multicenter retrospective review was performed analyzing 1081 primary total hip replacements in 944 patients using the Harris Galante-I cementless acetabular component with screw fixation. All patients were followed up for a minimum of 5 years with a mean followup of 81 months. Linear polyethylene wear averaged 0.11 mm/year (range, 0-0.86 mm/year). Pelvic osteolysis was seen in 25 patients (2.3%). Migration of the acetabular component was seen in four hips. A subgroup of patients was reanalyzed at a minimum followup of 10 years. The mean linear polyethylene wear rate remained 0.11 mm/year. In this group, only one socket had migrated. There was an association between wear rate and age. On average, younger patients had higher wear rates. The risk for having pelvic osteolysis develop and the need for revision surgery also was age-related. Twenty-two percent of hip replacements (15 hips) in patients younger than 50 years of age at the time of their index operation had pelvic osteolysis develop. In contrast, for patients older than 50 years of age at the time of surgery only 7.8% (eight hips) had osteolysis of the pelvis develop. For patients older than 70 years of age at the time of primary total hip replacement, none had pelvic osteolysis develop.

Primary Total Hip Arthroplasty Using an Anterior Approach and a Fracture Table Short-term Results From a Community Hospital

There are no data regarding the efficacy and safety of minimally invasive hip arthroplasty technique performed by community practice orthopedists. The early clinical and radiographic results of primary total hip arthroplasty using a minimally invasive anterior approach to the hip performed on a fracture table were studied. Two hundred thirty-one consecutive patients (247 hips) of 5 community practice surgeons were studied. The average surgical time (164 minutes) and estimated blood loss (858 mL) were more than double, and the major complication rate (9%) was 6 times that reported by an innovator of the procedure. However, no postoperative dislocations occurred. Adequate training is critical to reduce the risk of complications during the learning experience of minimally invasive hip arthroplasty procedures by community practice surgeons.

A clinical−pathologic−biochemical study of the membrane surrounding loosened and nonloosened total hip arthroplasties

The clinical and roentgenologic data from 31 excised components from 19 revision arthroplasty cases were correlated with the histology and biochemistry of the membrane at the bone-cement or bone-prosthesis interface. Twenty-seven components were cemented and four were uncemented. Twenty-four implants were clinically and roentgenologically loose, one was possibly loose, and six were well fixed. Loose components, whether cemented or not, demonstrated statistically higher prostaglandin E2 levels in the surrounding membrane compared to the nonloose group. Collagenase and M-collagenase levels were absent or insignificantly low in all specimens; no detectable interleukin 1 beta was found. This suggests that prostaglandin E2 may be associated with the bone lysis associated with prosthesis loosening.

Fatigue fracture of a forged cobalt-chromium-molybdenum femoral component inserted with cement : A report of ten cases

Ten patients who had had a total hip replacement with a forged cobalt-chromium-molybdenum femoral prosthesis (Precoat or Precoat Plus) inserted with cement were seen with a fatigue fracture of the stem an average of fifty months (range, nineteen to seventy-four months) postoperatively. The average age of the patients was sixty-one years (range, forty-three to seventy-three years), and the average weight was ninety-six kilograms (range, seventy to 130 kilograms). Eight patients had had a primary total hip replacement, and two had had a revision; all of the acetabular components had been inserted without cement. Radiographs that had been made before the fracture were available for four of the eight hips that had had a primary replacement; all four had radiographic evidence of debonding of the cement mantle from the proximal end of the stem. This probably caused exaggerated cantilever bending stresses on the proximal aspect of the stem as the distal end of the stem was well fixed. The radiographs of both hips that had had a revision demonstrated a non-union of the greater trochanter, which had resulted in separation at the cement-bone interface at the proximal portion of the femur before the fracture. Scanning electron micrographs of five of the ten fractured prostheses demonstrated a fatigue fracture that began near the anterolateral corner of the prosthesis, through characters that had been etched on the implant with a laser. Metallurgical analysis indicated subsurface voids or inclusions, or both, immediately under the region that had been etched. This finding is consistent with thermal changes to the microstructure of the alloy that probably caused a focal reduction in the material strength. A high proportion (seven) of the ten stems had a poor cement mantle. Also, of the seven small stems that were used, six had been implanted in patients who weighed more than eighty kilograms, so there was relative undersizing of the prostheses. Early debonding of the proximal end of a Precoat femoral prosthesis from the cement mantle may occur as a result of a thin cement mantle, leading to loosening and possibly to early fatigue fracture of the stem if the distal portion of the stem remains solidly fixed in the distal portion of the cement column. On the basis of our experience, we recommend that patients who have radiographic evidence of a debonded Precoat femoral component should be informed of the risk of fatigue fracture of the stem and be followed closely even though there may be no symptoms of loosening of the femoral component.

Increasing incidence of femoral osteolysis in association with uncemented Harris-Galante total hip arthroplasty. A follow-up report.

Sixty-nine consecutive uncemented total hip arthroplasties were performed in 59 patients using the Harris-Galante prosthesis (Zimmer, Warsaw, IN). The patients were reviewed an average of 44 and 71 months after surgery. Patients in whom femoral osteolysis was identified at the time of the first review were again evaluated at the second review to determine if the size of the osteolytic lesion had increased over time. At the initial review an average of 44 months postsurgery, the overall incidence of femoral osteolysis was 22%. At the second review, the incidence of femoral osteolysis had increased from 22 to 52%. Two thirds of the lytic lesions diagnosed at the time of the first review had increased in size. This study demonstrated that the incidence of femoral osteolysis in cementless hip arthroplasties increases with time and that the majority of existing lesions enlarge over time. Once lesions are identified, more frequent follow-up evaluations are recommended. Revision surgery may be required for progressive femoral osteolysis, despite the absence of significant clinical symptoms.

Loosening and osteolysis of cemented joint arthroplasties : A biologic spectrum

The purpose of this study was to characterize the cell types (using immunohistochemistry) and cytokine expression (using in situ hybridization) of tissues surrounding well fixed and loose cemented prostheses undergoing revision. Clinical and radiographic data were gathered prospectively for a series of cemented total joint replacements undergoing revision. Three groups were identified: (1) loose implants with osteolysis (10 specimens), (2) loose implants without osteolysis (11 specimens), and (3) well fixed implants (7 specimens). At surgery, a specimen was harvested from the bone cement interface. Immunohistochemical staining was performed using monoclonal antibodies to identify macrophages and lymphocyte subgroups. Human antisense probes were selected to identify the mRNA for specific cytokines using in situ hybridization. The percentage of positively staining cells was determined for each antibody or probe using a grid counting technique. Tissues from loose cemented prostheses with osteolysis contained significantly greater numbers of macrophages and T lymphocytes compared with tissues from loose and well fixed cemented prostheses without osteolysis. The number of interleukin-1 and interleukin-6 positive cells was highest in specimens with osteolysis and lowest in specimens from well fixed prostheses. These cytokines modulate the growth and differentiation of cells in the immune system and the monocyte and macrophage system and mediate the remodeling of bone and mesenchymal tissues. Specific cell populations and cytokine profiles appear to be involved in periprosthetic osteolysis; this information may be useful in planning strategies for prevention and treatment.

Postoperative blood salvage using the Cell Saver after total joint arthroplasty.

The purpose of this study was to investigate whether the salvage in the recovery room of blood from the drainage tubes of patients who had total joint arthroplasty was both feasible and efficacious. The cases of seventy-four patients who had seventy-six consecutive total hip or knee arthroplasties were studied prospectively. Intraoperative salvage of blood was performed using the Cell Saver. After closure of the fascial layer or joint capsule, the drainage tubes were connected to the Cell Saver in the operating room and remained connected in the recovery room for a mean of 2.9 hours. Blood that was collected in the recovery room was then processed and transfused back to the patient. The average amount of blood that was salvaged after different types of arthroplasty varied. The addition of bone cement to the acetabular side during primary total hip replacement decreased the amount of postoperative bleeding and of salvaged blood (p = 0.018), whereas cementing the femoral component had no statistically significant effect. Revision total hip replacement also resulted in more bleeding and in the collection of more blood in the recovery room than did primary total hip replacement (p = 0.03), especially if cement was not used (p less than 0.001). There were no statistical differences in the amount of blood that was collected in the recovery room after unilateral, bilateral, primary, or revision total knee replacement.(ABSTRACT TRUNCATED AT 250 WORDS)