Dual proline labeling protocol for individual "baseline" and "response" biosynthesis measurements in human articular cartilage.

OBJECTIVE: The heterogeneity of biosynthesis in human-derived cartilage explants poses a challenge to its use in experiments. The aim of this study was to determine the consistency with which two consecutive measures of biosynthesis could be made in individual human articular cartilage explants using a dual proline radiolabeling protocol. METHODS: Full-thickness cartilage explants were harvested from young bovine or human (total knee replacement) tibial plateaus. Two consecutive measurements of biosynthesis were obtained by measuring (3)H-proline and (14)C-proline incorporation. Each sample's ratio of (14)C-/(3)H-proline incorporation was computed. For comparison to traditional experimental designs, the (14)C-proline incorporation ratio was computed for adjacent cartilage samples. The number of samples needed to observe a change in the proline incorporation ratio of 10, 20, and 50% was determined for both methods. RESULTS: The dual-label ratio was consistent across samples from the same plateau [95% confidence interval (CI): +/-20% (human) and +/-30% (bovine) of median]. Adjacent human sample pairs had much greater variability in their (14)C-proline incorporation (95% CI: +/-50% of median). Adjacent bovine sample pairs had CIs that were similar in magnitude to those for the dual-label approach. In the human plateaus, ratio changes of 10, 20 and 50% could be detected using dramatically fewer samples than the adjacent pair method. For bovine samples, the two methods required a similar number of samples per group. CONCLUSION: The consistency of the dual-label approach may overcome the difficulties in studying the effects of interventions on biosynthesis in human cartilage in vitro.

Role of cell-matrix interactions in osteoclast differentiation.

Osteoclast and their mononuclear cell precursors are present within the bone microenvironment at sites of physiologic and pathologic bone resorption. Analysis of tissues from sites of bone resorption reveal that cells expressing the full morphological and functional properties of mature osteoclasts are restricted to the immediate bone surface. We hypothesize that in addition to cytokines, components of the bone matrix and specific cell surface receptors on osteoclasts and their precursors play an essential role in determining the genetic profile and functional properties of fully differentiated resorbing osteoclasts. We have employed expression profiling, with an in vitro model of matrix-dependent osteoclast differentiation, to identify the molecular pathways by which bone matrix-interactions induce terminal osteoclast differentiation and activation. In preliminary studies, we have identified unique genes and transcriptional pathways that are induced by interaction of osteoclast precursors with specific components of the mineralized bone matrix. The authenticity of the gene profiles, as markers of osteoclast differentiation and activation, have been provisionally validated using an in vivo animal bone implantation model and by examination of tissues from patients with specific forms of pathologic osteoclast-mediated bone resorption. The ultimate goal of our studies is to identify new molecular targets for inhibiting osteoclast-mediated bone loss in disorders of pathologic bone loss. The early work of Walker et al. (Walker 1972) in parabiotic animals, and the subsequent studies of Burger et al. (Burger, Van der Meer, van de Gevel, et al. 1982) using a co-culture model with fetal bone rudiments and bone marrow-derived cells, have helped to establish that osteoclasts are derived from macrophage precursors of colony forming unit-macrophage (CFU-M lineage). As such, they share a common hematopoietic origin with other CFU-M lineage cells, including tissue macrophages that populate the lung (alveolar macrophages), liver (Kupfer cells), synovium (synovial macrophages) and other organs. They also share a common lineage

Autologous blood donation and subsequent blood use in patients undergoing total knee arthroplasty.

Autologous blood donation is designed to avoid complications from allogeneic blood, leaving units of blood in the general blood supply. It is unclear how efficient these programmes are in accomplishing these goals. It is unclear if autologous donation provokes increased need for any transfusion following surgery and whether it can be avoided in low-risk surgeries. Of 430 patients undergoing unilateral primary knee replacement arthroplasty over 12 months in our hospital, 309 had autologous donations and 121 did not. Of the 121 patients who did not donate, 36% completed surgery without transfusion, whereas only 17% of those who had autologous donations did so (P < 0.05). Age less than 65 years, higher baseline and postoperative haemoglobin levels were associated with lower transfusion rates. Patients who had autologous donations were approximately four times more likely to be transfused. As the number of autologous units donated increased, transfusions following surgery increased. Autologous donation did reduce allogeneic blood transfusions. Therefore, autologous blood donation for unilateral total knee arthroplasty is associated with overall increased transfusion rates, but with reduced need for allogeneic blood, independent of other clinical factors associated with transfusion. Therefore, there is need for reconsideration of these programmes relative to specific surgeries.

Transmission electron microscopy of intracellular particles of polyethylene from joint replacement prostheses: size distribution and cellular response.

The objectives of this transmission electron microscopy study of peri-implant tissues retrieved at revision arthroplasty were to (1) determine the size distribution of intracellular polyethylene particles, and (2) assess the cellular response to phagocytosed polyethylene particles as revealed by the condition of the cellular organelles. The frequency distributions of intracellular polyethylene particle sizes for 15 cases of total hip replacement showed that more than 75% of the particles had lengths of less than 0.5 microm. More than 90% of the particles were less than 1.0 microm in size. In comparison, the frequency distribution for the particles in cellscomprising tissue retrieved from three total knee replacement prostheses showed that only 43% of the particles were less than 0.5 microm in length and 72% were less than 1 microm in size. There was no statistically significant difference in the mean particle length between the specimens from the hip and knee patients. The majority of the cells containing polyethylene were without signs of degeneration. The cytoplasmic and nuclear membranes were intact. Several electron lucent voids which once contained polyethylene particles were seen surrounded by several healthy appearing mitochondria, which displayed sharp membranes and intact cristae. There were no signs of a cytotoxic response to polyethylene at the ultrastructural level.

Particulate bone grafting of osteolytic femoral lesions around stable cementless stems.

The purpose of the current study was to evaluate the effect of particulate grafting for proximal femoral osteolysis in the presence of a well-fixed cementless femoral stem at the time of acetabular liner change or revision. Sixteen patients (17 hips) who averaged 51 years of age underwent curettage and packing of proximal femoral osteolytic lesions with cancellous allograft. Modular acetabular liners were changed in 11 patients, acetabular revisions were performed in six patients, and femoral heads were exchanged in all patients. The femoral component was retained in all patients. The majority of patients were asymptomatic before revision surgery. The size of the femoral osteolytic lesions was measured preoperatively and postoperatively with anteroposterior and Lauenstein lateral radiographs of the hip. Preoperatively, the average lesion was 41 x 16 mm on the anteroposterior view and 18 x 7 mm on the lateral view. The average clinical and radiographic followup was 39 and 32 months, respectively, with a minimum followup of 24 months. All but one patient remained asymptomatic during the followup period and no femoral stem showed evidence of loosening. The size of the femoral osteolytic lesion averaged 16 x 6 mm on the anteroposterior view and 6 x 2 mm on the lateral view at most recent followup. In 15 of 17 patients, the size of the femoral lesion had regressed. This technique seems to be a viable means of preventing progressive osteolysis and femoral loosening while preserving bone stock for future reconstruction.

Effect of low-friction ion-treated femoral heads on polyethylene wear rates.

Polyethylene wear is a major contributor to osteolysis and subsequent aseptic loosening of prosthetic components in total hip arthroplasty. Use of ion implantation as a surface modification to the metallic bearing component of orthopaedic implants may be an effective means of reducing wear debris at the bearing interface. In July 1991, low friction ion treated femoral heads were introduced. This study evaluates the effect of the low friction ion treated femoral head on polyethylene wear. Fifty-five total hip arthroplasties (53 patients) with low friction ion treated femoral heads followed up a minimum of 3 years were matched with 55 total hip arthroplasties (47 patients) without low friction ion treated femoral heads for the same postoperative period. Socket wear was evaluated radiographically. Case matching and strict inclusion criteria were used to control for known factors influencing polyethylene wear. These criteria included: (1) cases matched for gender and age within 2 years; (2) diagnosis limited to osteoarthritis or avascular necrosis of the femoral head only; (3) femoral head diameter limited to 26 or 28 mm only; (4) hydroxyapatite coated femoral stem of the same design and a metal backed socket of the one of two designs with the same polyethylene insert; and (5) minimum followup of 3 years. The linear wear rate of polyethylene was 0.161 +/- 0.095 mm per year in the group without the low friction ion treated heads and 0.116 +/- 0.101 mm per year in the low friction ion treated group. The volumetric wear rates were 74.5 +/- 44.3 mm3 per year for the group without the low friction ion treated heads and 57.8 +/- 51.1 mm3 per year for the low friction ion treated group. Assuming the sensitivity of these measurements can detect these small differences in wear accurately, these results suggest low friction ion treated prosthetic heads are useful in reducing polyethylene wear at 3-year minimum followup.

An analysis of blood management in patients having a total hip or knee arthroplasty.

Three hundred and thirty orthopaedic surgeons in the United States participated in a study of transfusion requirements associated with total joint arthroplasty. A total of 9482 patients (3920 patients who had a total hip replacement and 5562 patients who had a total knee replacement) were evaluated prospectively from September 1996 through June 1997. Of those patients, 4409 (46 percent [57 percent of the patients who had a hip replacement and 39 percent of the patients who had a knee replacement]) had a blood transfusion. Two thousand eight hundred and ninety patients (66 percent) received autologous blood, and 1519 patients (34 percent) received allogenic blood. Ordered logistic regression analysis showed the most important predictors of the transfusion of allogenic blood to be a low baseline hemoglobin level and a lack of predonated autologous blood. Preoperative donation of autologous blood decreases the risk of transfusion of allogenic blood; however, inefficiencies in the procedures for obtaining autologous blood were identified. Sixty-one percent (5741) of the patients had predonated blood for autologous transfusion, but 4464 (45 percent) of the 9920 units of the predonated autologous blood were not used. Primary procedures and revision total knee arthroplasty were associated with the greatest number of wasted autologous units. Of the 5741 patients who had predonated blood, 503 (9 percent) needed a transfusion of allogenic blood. The frequency of allogenic blood transfusion varied with respect to the type of operative procedure (revision total hip arthroplasty and bilateral total knee arthroplasty were associated with the highest prevalence of such transfusions) and with a baseline hemoglobin level of 130 grams per liter or less. Transfusion of allogenic blood was also associated with infection (p < or = 0.001), fluid overload (p < or = 0.001), and increased duration of hospitalization (p < or = 0.01). These latter findings warrant further evaluation in controlled studies.

Intermediate clinical follow-up of a dual-radius acetabular component.

In this study, 92 primary total hip arthroplasties were performed in 83 patients using a porous-coated, dual-radius, cementless, acetabular component. All hips underwent line-to-line dome reaming with press-fit implantation that was judged to have complete bone contact. This acetabular shell provides a 1-mm oversized peripheral rim, which adds excellent initial stability while allowing complete bone contact in all hips. No fractures occurred. In 83% of hips, adjunctive screw fixation was not necessary. At a minimum of 4 years, follow-up, there were no revisions, no acetabular migration, one case of acetabular erosion consistent with osteolysis, and the average Harris Hip Score was 95. The design features of this new acetabular component have provided excellent fixation with complete initial bone contact, resulting in satisfactory intermediate clinical and radiographic results. The design provides excellent peripheral stability and complete bone contact.

Removal and reinsertion of cemented femoral components during acetabular revision.

A retrospective review examined all patients who underwent removal and reinsertion of a cemented femoral component during isolated acetabular revision by one surgeon since 1981. All components were reinserted into the original, intact cement mantle. Forty-two hips with 2- to 10-year follow-up periods were reviewed. Average follow-up period since revision was 67 months. Average followup period since index procedure was 191 months. Average Harris hip score increased from 61 before surgery to 90 at follow-up examination. Two femurs are definitely loose by Harris criteria, but both are asymptomatic. One solidly fixed femoral component was revised because of joint instability. Two hips have postrevision cement fractures. One patient has mild thigh pain. In vitro testing of eight cadaver hips showed no increase in rotational micromotion following removal and reinsertion. It is concluded that this technique aids in isolated acetabular revision surgery by avoiding the complications of trochanteric osteotomy and femoral revision, improving acetabular exposure, and decreasing operative time with minimal risk of disrupting femoral component fixation.

Surgical considerations and planning for acetabular and femoral deficiencies in revision hip replacement.

Cementless revision total hip arthroplasty provides a method for augmenting and restoring the remaining bone stock in a failed total hip arthroplasty. Careful preoperative planning, precise intraoperative technique and an adequate prosthetic inventory are required. Classification systems for bone deficiencies aid in planning grafting and prosthetic needs and in reviewing postoperative results. New cementless technology should provide even more satisfying results.

Use of TARA hemiarthroplasty in advanced osteonecrosis.

The results of 25 TARA hemiarthroplasty procedures performed on 21 patients with radiographically documented Ficat stages III and IV osteonecrosis are reported. The average patient age at the time of surgery was 37.6 years (range, 22-55 years). The average length of follow-up study was 37 months (range, 25-60 months). Preoperative Harris hip scores averaged 51 points (range, 22-69 points). Postoperative scores averaged 90 points (range, 66-100 points). Good or excellent results were obtained in 22 of 25 hips. There were no cases of infection or component dislocation. Three component revisions were performed in two patients. Four patients required removal of trochanteric wires and one patient had excision of heterotopic ossification. This procedure appears to offer selected young patients with advanced femoral head osteonecrosis a very satisfactory initial result, while preserving many options for subsequent revision procedures.

Bone scanning in the assessment of patellar viability following knee replacement.

In an attempt to diagnose avascular necrosis (AVN) of the patella, a potential complication of the surgical procedure, 99mTc-MDP bone scanning was performed pre- and postoperation in 37 patients treated by 41 total knee arthroplasties. The normal immediate postoperative scan should demonstrate increased radionuclide uptake in the patella when compared to preoperative scans. Decreased uptake was seen in four cases in the early postoperative period. This latter group was believed to be at risk for osteonecrosis and stress fracture of the patella. For this reason, prophylactic restriction of activity was instituted, with subsequent return of normal radionuclide uptake in the patella. Bone scanning provides an effective method of early diagnosis of patients at risk for the development of AVN and secondary patellar fractures following total knee arthroplasty.

Hip arthroplasties in Gaucher's disease.

In six patients with Gaucher's disease, arthroplasties were performed on ten hips for avascular necrosis of the femoral head. The follow-up ranged from two to twelve years. There were three Vitallium mold (cup) arthroplasties, seven primary total hip-replacement arthroplasties, and two revisions of total hip-replacement arthroplasties. Increased intraoperative and postoperative bleeding was often encountered. The cup arthroplasties yielded good results on long-term follow-up, but there was a high rate of loosening of the prosthetic components in the total hip replacements. There was one postoperative pathological fracture but there were no infections.

Conversion of mgh hemiarthroplasty of the knee to total knee arthroplasty using custom tibial components.

Hemiarthroplasty of the knee, similar to that of the hip, is frequently accompanied by the late development of pain associated with erosion of the metallic implant through opposing cartilage and bone. The authors present two patients (3 cases) in which MGH condylar hemiarthroplasty of the knee was treated for this problem by the addition of custom tibial components rather than complete revision to a modern total knee replacement device. The method is presented not as a treatment of choice, but as an alternative to complete revision (requiring the removal of additional femoral bone stock and possibly the need for a more constrained device) which provided relief of symptoms without accelerated wear of prosthetic components in a small number of knees.

Trochanteric osteotomy: analysis of pattern of wire fixation failure and complications.

Problems and complications following trochanteric osteotomy in 277 total hip replacements demonstrated that while the value of trochanteric osteotomy is obvious, the incidence of problems and complications in 277 total hip replacements was about 15%. Analysis was made of the location and sequence of wire failure following different techniques of trochanteric wiring. The usual method of wire failure was by fatigue fracture, although early fracture in the post-operative phase may be secondary to tensile failure, The incidence of wire tensile failure can be increased by inadvertent kinking or scoring of the wire during trochanteric fixation. An ununited trochanter should be protected against wire failure and its sequelae.