Showing papers in "Clinical Orthopaedics and Related Research in 1996"

Complications of Iliac Crest Bone Graft Harvesting

Abstract: Autologous bone grafts harvested from the iliac crest are commonly used in reconstructive orthopaedic surgery. Autologous bone is used to help promote bone healing in fractures and to provide structural support for reconstructive surgery. The results of autologous bone grafting are more predictable than the use of xenografts, cadaveric allografts, or synthetic bone substitutes because autologous bone grafts provide osteoinductive and osteoconductive properties, are not immunogenic, and are usually well incorporated into the graft site. In a retrospective review of 414 consecutive cases of iliac crest bone graft procedures performed at Brooke Army Medical Center from 1983 to 1993, 41 (10%) minor and 24 (5.8%) major complications were identified. Minor complications included superficial infections, superficial seromas, and minor hematomas. Major complications included herniation of abdominal contents through massive bone graft donor sites, vascular injuries, deep infections at the donor site, neurologic injuries, deep hematoma formation requiring surgical intervention, and iliac wing fractures. Harvesting of iliac crest bone graft can be associated with significant morbidity. However, with adequate preoperative planning and proper surgical technique, the incidence of these complications can be reduced.

Long-term results of allograft replacement in the management of bone tumors.

Abstract: Over the past 24 years, the authors have implanted >870 massive frozen cadaveric allografts mostly for the treatment of defects created by the resection of a bone tumor. Most of the grafts were obtained from the authors' institutional bone bank. The results show that only stage and type of graft affected outcome predictably. Specifically, grafts for a Stage 2 or Stage 3 tumor had a poorer outcome than those for Stages 0 and 1. The results for allograft arthrodeses were considerably poorer than osteoarticular, intercalary, and allograft plus prosthesis. The other major factors in results were complications--recurrence, infection, fracture, and nonunion--with the former 2 having a profound negative effect on outcome. After the first year of susceptibility to infection (10%) and the third year of increased risk of fracture (19%), the grafts become stable, and approximately 75% are retained by patients and are considered to be successful for >20 years after implantation. Osteoarthritis becomes a problem at approximately 6 years for osteoarticular grafts, and so far, 16% of the patients with distal femoral, proximal tibial, or proximal femoral grafts have required total joint replacements. Although the current results are adequate, they are imperfect, and research should be directed at improving the results.

Rabbit articular cartilage defects treated with autologous cultured chondrocytes.

Abstract: Adult New Zealand rabbits were used to transplant autologously harvested and in vitro cultured chondrocytes into patellar chondral lesions that had been made previously and were 3 mm in diameter, extending down to the calcified zone. Healing of the defects was assessed by gross examination, light microscope, and histological-histochemical scoring at 8, 12, and 52 weeks. Chondrocyte transplantation significantly increased the amount of newly formed repair tissue compared to that found in control knees in which the lesion was solely covered by a periosteal flap. In another experiment, carbon fiber pads seeded with chondrocytes were used as scaffolds, and repair significantly increased at both 12 and 52 weeks compared to knees in which scaffolds without chondrocytes were implanted. The histologic quality scores of the repair tissue were significantly better in all knees in which defects were treated with chondrocytes compared to knees treated with periosteum alone and better at 52 weeks compared to knees in which defects were treated with carbon scaffolds seeded with chondrocytes. The repair tissue, however, tended to incomplete the bonding to adjacent cartilage. This study shows that isolated autologous articular chondrocytes that have been expanded for 2 weeks in vitro can stimulate the healing phase of chondral lesions. A gradual maturation of the hyalinelike repair with a more pronounced columnarization was noted as late as 1 year after surgery.

Core decompression versus nonoperative management for osteonecrosis of the hip.

Abstract: A complete review of the literature disclosed that there were 42 reports of 2025 hips treated by either core decompression (1206 hips) or nonoperative management (819 hips), excluding electrical stimulation, for osteonecrosis of the femoral head. The peer-reviewed published reports included general surveys, prospective studies, and multicenter studies, but excluded case reports. Satisfactory clinical results were reported in 63.5% of hips in 24 studies of core decompression and in 22.7% of hips in 21 studies of nonoperative management. When looking at only precollapse hips, there were 71% versus 34.5% good results, respectively. Recalculation excluding reports by the 4 centers that do the most core decompressions (and report the best results) showed a clinical success rate for core decompression of 53% versus 22.7% for the nonoperatively treated group. Investigators of multiple studies have reported that nonoperative management leads to extremely poor results. Core decompression has been reported to have a notable effect on the natural history and clinical progression in early stages of osteonecrosis of the femoral head. In view of the limitations of this data, further clarification of this effect only can be obtained by large prospective randomized studies.

Role of bone substitutes.

Abstract: Approximately 500 million years ago, the Paleozoic era heralded an evolutionary marvel : the skeleton. Unique to this evolutionary development was the capacity for regeneration : the physiologic renewal of embryologically derived tissue. Many of the cellular and molecular components for bone regeneration have been identified (bone morphogenetic proteins), and their therapeutic manipulation will become common clinical practice. Moreover, synthetic materials produced in the laboratory and novel bone derivatives will be used to exploit the skeleton's capacity to regenerate and repair. The concept of repair may be viewed as the restoration of form and function to deficient osseous tissue. Materials that provoke repair can be categorized broadly as bone substitutes. In this review, bone substitutes are grouped into 2 categories, polymers and ceramics, and each is subclassified as biodegradable or nonbiodegradable. Examples of these materials are provided as well as some of their liabilities and virtues.

Rotational Landmarks and Sizing of the Distal Femur in Total Knee Arthroplasty

Abstract: In 100 knees undergoing a total replacement, the angles between the tangent line of the posterior condylar surfaces, the anteroposterior axis as described by Whiteside, the transepicondylar line, and the trochlear line were measured. Also measured were the sulcus angle, the transepicondylar width, the height of the condyles, and the thickness of the various cuts. Radiologic measurements made were: the mechanical angle, the hip center-femoral shaft angle, the transcondylar angle, and the tibial plateau-tibial shaft angle. The mean values of these measurements were calculated, and comparisons were made according to gender and the mechanical axis using the Student's t test. Correlations between the various measurements were calculated. The transepicondylar axis was found to be a reliable landmark to properly rotate the femoral component, and was easier to locate at surgery than the anteroposterior axis. In trochlear dysplasia and in some valgus knees, relying on the anteroposterior axis can induce an excessive external rotation of the femoral component, and the opposite can happen in some varus knees. The anterior extent of the condyles is highly variable in arthritic knees, and cannot be used to orient the prosthesis. The ratio between the transepicondylar width and the height of the condyles is constant, but some narrow femora could require narrower implants to avoid medial-lateral overhang of the femoral component.

Metal on Metal Surface Replacement of the Hip

Abstract: The historical failure of surface replacement has been due to the production of wear debris with subsequent bone resorption, loosening, and failure. To avoid these problems, a surface replacement using a metal on metal bearing allowing thin components and femoral design and instrumentation to avoid

Metal on Metal Surface Replacement of the Hip: Experience of the McMinn Prosthesis

Abstract: The historical failure of surface replacement has been due to the production of wear debris with subsequent bone resorption, loosening, and failure. To avoid these problems, a surface replacement using a metal on metal bearing allowing thin components and femoral design and instrumentation to avoid varus alignment has been designed. Two hundred thirty-five joints have been resurfaced with this prosthesis in almost 5 years. There have been no femoral neck fractures and no dislocations. There have been 4 designs differing in the method of fixation. In the press fit group, 6 of 70 hips had to be revised for aseptic loosening. In the cemented group, debonding of the cup occurred in 3 of 43 cases. Six patients had hydroxyapatite coated components and have had excellent clinical outcomes. The current design uses a peripherally expanded hydroxyapatite coated cup and a cemented metal head ; 116 of this design have been implanted during a 19-month period with excellent outcome. Despite short followup the authors are hopeful that the combination of a polar metal on metal bearing with appropriate fixation will yield a method of preserving bone stock in the younger patient requiring arthroplasty.

Periprosthetic fractures of the femur. An analysis of 93 fractures.

Abstract: A retrospective review of 93 periprosthetic fractures and 102 periprosthetic fracture treatments showed that the type of prosthesis (cemented, ingrowth, Austin-Moore) and the presence of preexisting stress risers play a role in determining where the fractures occur. The site of fracture and the prefracture interface influence treatment of periprosthetic fractures. This study suggests that fractures associated with a loose interface, cemented or cementless, are best treated by removal of the prosthesis, reduction of the fracture, and insertion of a long stemmed prosthesis with additional fixation as needed. Treatment of a periprosthetic fracture associated with a stable prosthesis depends on the site of fracture. Fractures proximal to the tip of a fixed prosthesis usually can be treated nonoperatively or with limited internal fixation. Fractures at the tip of the prosthesis may be managed by revision or internal fixation, and fractures below the prosthesis can be managed operatively or nonoperatively.

In vivo knee kinematics derived using an inverse perspective technique.

Abstract: Sixty-four subjects having implanted and nonimplanted knees were studied using fluoroscopic videos. Each subject, flexing in the sagittal plane, performed successive deep knee bends under fluoroscopic surveillance. Femorotibial contact in the sagittal plane was then determined using image matching and discrete digitization. At full extension, the mean contact point of the normal and posterior stabilized implanted femurs was anterior to the tibial midpoint in the sagittal plane. The average position was 6.49 mm (+3 - +13 mm) for the normal knees and 0.30 mm (0 - +4 mm) for the posterior stabilized knees. The implanted posterior cruciate retaining and anterior cruciate ligament deficient knees differed from the other knee types. Their average initial contact was posterior. The average contact at full extension for the posterior cruciate retaining and anterior cruciate ligament deficient knees was -5.13 mm (-2 - -8 mm) and -5.45 mm (-2 - -14 mm), respectively. The femur of the normal knee contacts the tibia anterior to the midpoint in the sagittal plane in full extension and translates posteriorly during flexion. The femur of the posterior stabilized knee contacts the tibia anteriorly, slightly less than the normal knee, and rolls back posteriorly during flexion similar to normal knees. The femurs of the posterior cruciate retaining and anterior cruciate ligament deficient knees contact the tibia posterior in extension, but translate anteriorly during midflexion in a substantial number of cases, which is kinematically opposite of the normal knees. The abnormal anterior femoral translation observed in the posterior cruciate retaining knees may be a factor in the premature polyethylene wear seen in retrieval studies.

Internal fixation of unstable pelvic ring injuries.

Abstract: One hundred and seven unstable pelvic fractures were treated operatively. Reductions were graded by the maximal displacement measured on the 3 standard views of the pelvis. Criteria were: excellent 4 mm or less, good 5 to 10 mm, fair 10 to 20 mm, and poor more than 20 mm. Overall there were 72 excellent, 30 good, 4 fair, and 1 poor reduction. Ninety-five percent of all reductions were excellent or good. Open reduction and internal fixation within 21 days were associated with a higher percentage of excellent reductions than in reductions performed after 21 days (70% versus 55%). These differences were not statistically significant, however. Complications were infrequent using the techniques described.

Cobalt and Chromium Concentrations in Patients With Metal on Metal Total Hip Replacements

Abstract: There has been a resurgence of interest in the use of metal on metal bearings in total hip arthroplasty. Although the use of metal on metal bearing couples would eliminate or substantially reduce particulate polyethylene generation (depending on the presence or absence of polyethylene in the implant system), there is concern about the potential for increased particulate and ionic metal generation in comparison with polyethylene on metal bearings. These metallic degradation products may be transported away from the implant site and distributed systemically. Chromium concentrations in the serum and urine and cobalt concentrations in the serum were measured in subjects with cobalt chromium alloy metal on metal total hip replacements and in controls without implants. Eight subjects with long term (> 20 years) McKee-Farrar total hip replacements had 9-fold elevations in serum chromium, 35-fold elevations in urine chromium, and at least 3-fold elevations in serum cobalt concentrations in comparison with controls. Six subjects with short term (< 2 years) metal on metal surface replacement arthroplasties had 3-fold elevations in serum chromium, 4-fold elevations in urine chromium, and 4-fold elevations in serum cobalt concentrations in comparison with subjects with McKee-Farrar implants. Although the toxicologic importance of these trace metal elevations has not been established, serum and urine metal concentrations may be useful markers for the tribologic performance of metal on metal bearings.

In vivo wear of 3 types of metal on metal hip prostheses during 2 decades of use

Abstract: Wear was analyzed on 21 metal on metal hip replacements, including McKee-Farrar, Muller, and Ring, that were retrieved from patients after as many as 25 years. Light and scanning electron microscopy indicated that early wear included substantial third body abrasion, possibly from particles generated while scratches from the original polishing were being eradicated and from dislodged surface carbides. However, the main contact zones were eventually worn smoother than the original surfaces. Wear was quantified by digitizing the shapes of the components on a coordinate measuring machine and identifying those areas that deviated from the original spheric surface. On the femoral heads, wear was typically concentrated in the superomedial region, that is, on the load axis. Three cases also had substantial wear inferiorly, but there were no cases with circumferential (equatorial) wear. The long term wear rates averaged approximately 6 μm per year or less and produced an average of approximately 6 mm 3 of metallic wear debris per year or less. Wear rate tended to increase as clearance increased over the range of 127 to 386 μm, and a McKee-Farrar prosthesis with the extreme clearance of 1.7 mm wore approximately 16 times faster than the average, but there was no apparent relationship between clearance and time to revision. Larger McKee-Farrar balls had less volumetric wear, on average, than smaller balls, and the Muller balls had the greatest wear, which may have been due to contact with the edges of recesses machined into the bearing zones of the Muller cups.

Bone morphogenetic protein-2 : Biology and applications

Abstract: Bone morphogenetic protein-2 is a low molecular weight glycoprotein, classified as a morphogen. The sine qua non of bone morphogenetic protein is consistently reproducible induction of bone development in heterotopic sites. Bone morphogenetic proteins belong to the expanding transforming growth factor-beta superfamily. Bone morphogenetic protein-2 has pleiotropic functions that range from extraskeletal and skeletal organogenesis to bone generation and regeneration. Bone morphogenetic protein induced bone formation in postfetal life recapitulates the process of embryonic and endochondral ossification. Through recombinant gene technology, human bone morphogenetic protein-2 is available in almost unlimited amounts for basic research and clinical trials. Human bone morphogenetic protein-2 induces structurally sound orthotopic bone in a variety of experimental systems, including femoral defects in rats, tibial and ulnar defects in rabbits, femoral defects in sheep, mandibular defects in dogs, spinal fusion in dogs, and porous ingrowth in rats. Human bone morphogenetic protein-2 research extends to the fields of developmental biology, genetics, and evolution. Bone morphogenetic protein has been used successfully at the authors' institution to heal clinical nonunions and to achieve spinal fusion. This report reviews the current understanding of bone morphogenetic proteins in general and BMP-2 in particular and summarizes their potential applications.

Observations of the function of the shoulder joint. 1944

Abstract: Observations of the Function of the Shoulder Joint Verne Inman;J. Saunders;Leroy Abbott; Clinical Orthopaedics and Related Research

Acetabular and femoral reconstruction with impacted graft and cement

Abstract: Loosening of primary cemented and noncemented components of total hip arthroplasties always is accompanied by a loss of bone stock. There are several options for reconstruction of the acetabular and femoral defects. The authors' treatment of choice is a standardized cemented revision procedure with tight impaction of morsellized cancellous autograft or allograft chips in acetabular and femoral reconstructions. In this study, the clinical and radiographic evaluation of acetabular defects reconstructed with impacted morsellized allograft femoral heads was described. A cemented cup supplemented with morsellized cancellous grafts and wire meshes in cases of segmental defects was sufficiently stable to allow for complete graft consolidation. After a mean followup of 70 months of 88 hips, 4 cases of clinical failures (including 1 infection) and 6 cases of radiologic failure of the reconstructions were observed, resulting in a failure percentage of 11.4% after 5 years. Autografts and allografts were equally effective. Because the clinical success of the technique also was supported by the results of histologic and biomechanic studies in animals, the authors were encouraged to continue this technique, not only in the acetabulum, but also in the femur.

Tissue reaction to metal on metal total hip prostheses

Abstract: The periprosthetic tissue reaction to polyethylene wear debris in metal on polyethylene total hip replacements is strongly implicated as the cause of osteolysis. This has led to a renewed interest in metal on metal total hip replacements. However, little is known about the role of wear debris in failures of these prostheses. Capsular and interface tissues from 9 long and short term metal on metal total hip replacement retrievals were studied to assess the tissue reaction around these prostheses. As compared with metal on polyethylene cases, the extent of the granulomatous inflammatory reaction and the presence of foreign body type giant cells was much less intense in metal on metal cases, likely because of the lower numbers and overall smaller size of metal wear debris particles. This may lead to a better transport of the particles from the joint tissues and a lower incidence of periprosthetic osteolysis around metal on metal hip replacement.

Cancer risk after metal on metal and polyethylene on metal total hip arthroplasty

Abstract: The incidence of cancer after metal on metal total hip arthroplasty (McKee-Farrar) and polyethylene on metal total hip arthroplasty (Brunswik, Lubinus) was compared with that of the general population in Finland. The mean followup time for the patients who had metal on metal total hip arthroplasty was 15.7 (9092 person years) and for the patients who had polyethylene on metal total hip arthroplasty it was 12.5 years (19,846 person years). One hundred thirteen malignant cancers were observed in patients who had metal on metal total hip arthroplasty and 212 were observed in patients who had polyethylene on metal total hip arthroplasty. The standardized incidence ratio for all cancers of the metal on metal arthroplasty group was 0.95 (95% confidence limits 0.79-1.13) and that of the polyethylene on metal arthroplasty group was 0.76 (95% confidence limits 0.68-0.86). The risk of total cancer in the patients who had metal on metal total hip arthroplasty was 1.23-fold compared with that of the patients who had polyethylene on metal total hip arthroplasty. Both groups had significantly less lung cancer than the general population: the leukemia incidence in the patients who had metal on metal total hip arthroplasty was slightly increased (observed to experienced 7/3.03, standardized incidence ratio 0.61; 95% confidence limits 0.17-1.56). The leukemia rate of the patients who had metal on metal total hip arthroplasty was 3.77-fold compared with that of the patients who had polyethylene on metal total hip arthroplasty, but this difference was not statistically significant. No sarcomas were observed at the site of the prosthesis. The incidence of the other forms of cancers did not differ significantly from those in the general population. The observed variation in the incidence of different cancers among patients who had total hip arthroplasty compared with the general population suggests that factors other than total hip arthroplasty play a major role in the origin of cancer.

The demographics of slipped capital femoral epiphysis. An international multicenter study.

Abstract: One thousand six hundred thirty children with 1993 slipped capital femoral epiphyses were reviewed; 41.2% were girls and 58.8% were boys. There were 47.5% white, 24.8% black, 16.9% Amerindian, 7.4% Indonesian-Malay, 2.1% Native Australian/Pacific Islands, and 1.3% Indo-Mediterranean children. The diseased hip was unilateral in 77.7% and bilateral in 22.3% of the children, and chronic in 85.5% and acute in 14.5% of the children. Of the unilateral slips, 40.3% involved the right hip and 59.7% the left hip. The child's weight was greater than or equal to the ninetieth percentile in 63.2% of the children. The average age for the girls and boys was 12 and 13.5 years. The age at diagnosis decreased with increasing obesity. The youngest children were the Native Australian/Pacific Island children (11.8 years) and the oldest were the white and Indo-Mediterranean children (13 years). The Indonesian-Malay and Indo-Mediterranean children were the lightest in weight, and the black children the heaviest. The Indo-Mediterranean children had the highest proportion of boys (90.5%), and the Native Australian/Pacific Island children the lowest (50%). The highest percentage of bilaterality was in the Native Australian/Pacific Island children (38.2%), and the lowest in the Amerindian children (16.5%). The relative racial frequency of slipped capital femoral epiphysis compared with the white population was 4.5 for the Polynesian, 2.2 for the black, 1.05 for the Amerindian, 0.5 for the Indonesian-Malay, and 0.1 for the Indo-Mediterranean children. In children with unilateral involvement, the age at presentation was younger for those children in whom bilateral disease later developed (12 versus 12.9 years old). In 82% of the children with sequential bilateral slips, the second slip was diagnosed within 18 months of the first slip.

Factors affecting bone graft incorporation

Abstract: Successful graft incorporation requires that an appropriate match be made among the biologic activity of a bone graft, the condition of the perigraft environment, and the mechanical environment. The authors have studied, in a wide variety of animal models, the factors that affect the main components of bone graft incorporation: revascularization, new bone formation, and host-graft union. The principal determinant of the rate, pattern, and amount of revascularization is the presence or absence of a vascular pedicle. The nonvascularized bone graft is entirely dependent on the surrounding tissue for its revascularization, which results in a noticeable delay in vessel ingrowth. The principal determinant of the rate and amount of new bone formation on, in, or about a bone graft is the presence or absence of living, histocompatible, committed bone-forming cells. When living cells are not part of the graft at the time of implantation, the cells that form new bone are derived from host tissues, and new bone formation is delayed. The principal determinants of host-graft union are stability of the construct and contact between host bone and the graft. Factors that slow or inhibit all of these processes are reduction of the biologic activity of the graft by freezing or some other treatment, histocompatibility antigen disparities between donor and recipient, mechanical instability between the graft and the perigraft environment, and local and systemic interference with the biologic activity of the graft and surrounding tissue, for example, by irradiation or the administration of cisplatin. The task of the clinician who does a bone grafting procedure is to choose the right graft or combination of grafts for the biologic and mechanical environment into which the graft will be placed.

Allograft Versus Autograft Anterior Cruciate Ligament Reconstruction: 3- To 5-year Outcome

Abstract: Sixty-four patients whose knees underwent anterior cruciate ligament reconstruction with nonirradiated allograft tissue were compared with 26 patients whose anterior cruciate ligaments were reconstructed using autograft tissue 3 to 5 years after their operation. Detailed symptoms, activity-level, and functional outcomes, physical examination, and instrumented knee testing were recorded. No statistically significant differences were found except a higher incidence of loss of terminal extension in the autograft group. These differences were small and not considered clinically significant. Laxity and knee scores were similar in both groups. According to International Knee Documentation Committee ratings, overall outcome was normal or nearly normal in 48% of the allograft patients and in 38% of the autograft patients. Overall subjective rating with the Cincinnati Knee Score was 85.8 for the allograft patients and 84.5 for the autograft patients. Allograft tissue provides an acceptable alternative to autograft tissue for reconstruction of the anterior cruciate ligament.

2-stage reimplantation for infected total knee replacement.

Abstract: Between 1977 and 1983, 64 infected total knee replacements in 60 patients were treated with a 2-stage protocol for reimplantation. The clinical results and survivorship were determined at an average followup of 7.5 years (range, 2-17 years). Surgical protocol included removal of the prosthesis and all cement with thorough debridement of bone and soft tissues. This was followed by 6 weeks of parenteral antibiotics and then reimplantation of a new prosthesis. At followup, 6 knees (9%) had become reinfected, but only 2 with the same organism. Four knees had been revised : 3 for aseptic loosening and 1 for a periprosthetic femur fracture. Two other knees were impending failures due to aseptic loosening. The average Hospital for Special Surgery knee score was 78 points with 18 excellent, 28 good, 13 fair, and 5 poor results. Seventy-eight percent of patients were satisfied with the overall result of their reimplanted prosthesis and 95% think that they made the right decision in undergoing total knee arthroplasty. The 10-year predicted survivorship of 2-stage reimplantation is 77.4%. Two-stage reimplantation with a 6-week course of parenteral antibiotics is an effective means to eradicate deep infection and to provide a functional knee. The long term functional results and overall survivorship are comparable with the results of revision of aseptic failed total knee arthroplasty.

Metal on Metal Bearings in Hip Arthroplasty

Abstract: Periprosthetic osteolysis caused by wear debris released from the bearing surface of polyethylene components is the major problem in contemporary hip arthroplasty. Several types of metal on metal prostheses were developed in the 1960s, but by the mid 1970s they were completely displaced by polyethylene bearings. There have been several generations of all metal components with significant variation in design, tolerances, and bearing surface quality. A number of these hips have survived for more than 25 years because of low wear rates and minimal osteolysis. Identification of the characteristics that contributed to long term function is important. The historical development and clinical results of metal on metal hip arthroplasties are presented. Factors that led to the abandonment of the metal on metal bearings are related to : (1) the early success of the Charnley prosthesis ; (2) the frictional torque issue ; (3) carcinogenesis concerns ; (4) metal sensitivity concerns ; (5) high infection rates ; and (6) increased strain rates in periprosthetic bone and fatigue fractures of the acetabular floor. The accumulated experience to date enables one to evaluate all the factors with a different perspective and makes the use of newer metal on metal bearings a viable option in younger patients.

The demographics of slipped capital femoral epiphysis : an international multicenter study : Splipped capital femoral epiphysis

Abstract: One thousand six hundred thirty children with 1993 slipped capital femoral epiphyses were reviewed; 41.2% were girls and 58.8% were boys. There were 47.5% white, 24.8% black, 16.9% Amerindian, 7.4% Indonesian-Malay, 2.1% Native Australian/Pacific Islands, and 1.3% Indo-Mediterranean children. The diseased hip was unilateral in 77.7% and bilateral in 22.3% of the children, and chronic in 85.5 % and acute in 14.5% of the children. Of the unilateral slips, 40.3% involved the right hip and 59.7% the left hip. The child's weight was greater than or equal to the ninetieth percentile in 63.2% of the children. The average age for the girls and boys was 12 and 13.5 years. The age at diagnosis decreased with increasing obesity. The youngest children were the Native Australian/Pacific Island children (11.8 years) and the oldest were the white and Indo-Mediterranean children (13 years). The Indonesian-Malay and Indo-Mediterranean children were the lightest in weight, and the black children the heaviest. The Indo-Mediterranean children had the highest proportion of boys (90.5%), and the Native Australian/Pacific Island children the lowest (50%). The highest percentage of bilaterality was in the Native Australian/Pacific Island children (38.2%), and the lowest in the Amerindian children (16.5%). The relative racial frequency of slipped capital femoral epiphysis compared with the white population was 4.5 for the Polynesian, 2.2 for the black, 1.05 for the Amerindian, 0.5 for the Indonesian-Malay, and 0.1 for the Indo-Mediterranean children. In children with unilateral involvement, the age at presentation was younger for those children in whom bilateral disease later developed (12 versus 12.9 years old). In 82% of the children with sequential bilateral slips, the second slip was diagnosed within 18 months of the first slip.

Range of motion in total knee replacement.

Abstract: This is a multicenter prospective clinical study using a modified Knee Society scoring system which evaluated the effect of age, gender, weight, preoperative range of motion and knee score, previous surgery, and modification of the posterior femoral condyle geometry on postoperative range of motion. The primary outcome variable was change in flexion. The data were collected from 5 surgeons using a single total knee system. The current study has 621 patients enrolled, of which 282 total knee replacements have followup of 12 months and 86 have followup of 24 months. Multivariate analysis was used to evaluate the data. The variables listed were examined as to their relationship to changes in flexion. Patients were divided into 3 groups : preoperative flexion less than 90°, 91° to 105°, and greater than 105°. When comparing the patients with preoperative motion less than 90° to those with motion greater than 105°, the first group improved 26° more than the latter. They also improved 12° more than the midrange group. The midrange group improved 14° more than the upper range group. These values are all adjusted to eliminate differences due to the other variables. None of the other variables showed a significant correlation with the flexion outcome. To analyze the knee score, the group was also divided into 3 groups : preoperative score less than 27, 28 to 40, and greater than 40. The preoperative knee score was the best predictor of the postoperative knee score. The patients with preoperative knee scores below 27 improved 16 points more than those in the 27 to 40 range and 33 points greater than the greater than 40 group. To analyze functional evaluation, the patients were divided into 3 groups based on preoperative score : less than 40, 41 to 50, and greater than 50. Those in the less than 40 group improved 14 points more than the midrange group and 35 points more than the greater than 50 group. Analysis of delta range of motion and delta pain showed similar results. Age, weight, previous open surgical procedure, and altered femoral component contour, did not seem significantly correlated with changes in postoperative flexion. The best predictors of postoperative clinical results are the preoperative scores.

Glenohumeral stability. Biomechanical properties of passive and active stabilizers.

Abstract: The shoulder is characterized foremost by its mobility and large range of motion. The glenohumeral joint is notable for its relative lack of bony constraint, relying heavily on the congruent articulating surfaces and surrounding soft tissue envelope for static and dynamic stability. Effective function in the articulation is achieved by a complex interaction between the various articular and soft tissue restraints. The rotator cuff muscles center the humeral head in the congruent glenoid fossa through the midrange of motion, when the capsuloligamentous structures are lax. However, incongruent joints, especially in positions of loading asymmetry (in external rotation), have larger translations that occur at the extremes of motion. Excessive translations are then effectively restricted by the mechanical properties of the inferior glenohumeral ligament. When the capsule is tightened anteriorly it results in an anterior tether and causes an associated posterior shift in contact on the glenoid. The posterior migration of the humeral head center and glenohumeral contact are again more pronounced in shoulders with reduced congruence. Additional studies of normal motion in different planes, the effects of rotator cuff pathology and dysfunction on the kinematics of the joint, proprioception of the capsule, and biomechanical tests of the inferior glenohumeral ligament and other components of the joint capsule at strain rates associated with injury, need to be conducted to understand the specifics of normal shoulder function and the pathophysiologic processes that occur during shoulder degeneration.

Use of bone morphogenetic protein-2 in the rabbit ulnar nonunion model.

Abstract: The ability of the osteoinductive protein and recombinant human bone morphogenetic protein-2, combined with polylactic glycolic acid porous microspheres and autologous blood clot to heal a large segmental defect was tested in a rabbit diaphyseal defect model. Two centimeter nonuniting defects were surgically created in the bilateral ulnae of 50 male New Zealand white rabbits. Each defect was then implanted with a pastelike polylactic glycolic acid/blood clot combination that was mixed with 5 different concentrations of recombinant human bone morphogenetic protein-2. The forearms were radiographically assessed on a biweekly schedule for 8 weeks. At 8 weeks, all animals were sacrificed and forearms radiographed. Radiographs were then scored by 3 independent observers for bone formation and union rates. United limbs were tested in torsion for mechanical strength using a Burstein torsion tester. All nonunited limbs were analyzed histologically as were 2 united limbs from each dosage group. Radiographic evaluation revealed that there was a dose dependent response in healing of the ulnar defect with a higher bone formation rate in the 2 higher dose limbs than in the lower dose limbs. Union was achieved in 100% of the highest dose limbs, whereas only 50% of the lowest dose limbs achieved bony union. No defects implanted with carrier alone achieved union. Biomechanical studies revealed significantly stiffer bone than age matched controls. Histologic analysis demonstrated normal bone formation with abundant normal appearing osteoid. These dose response data further support the role of recombinant human bone morphogenetic protein-2 as a potent morphogen in bone regeneration.

Distribution of cobalt chromium wear and corrosion products and biologic reactions.

Abstract: Replacement hip arthroplasty with the use of ultrahigh molecular weight polyethylene for the cup articulating with a metal head has provided a low friction arthroplasty with years of success. However, the search for improved materials and designs for articulating surfaces continues. The use of metallic heads articulating with metallic cups is now being reconsidered for total hip replacements. Success will be enhanced if wear and corrosion of the articulating surfaces can be kept below that of the metal on ultrahigh molecular weight polyethylene couple. Concern has been raised about the release, and biologic fate, of metal species from corrosion and wear. Titanium alloys have been shown to have limitations as an articulating surface showing significant wear, and the alloy per se should not be considered for wear couples in total hip replacements. The cobalt chromium alloys are known to have reasonable wear and corrosion properties and continue to be evaluated. The issue of cobalt chromium wear and corrosion products and how this relates to the biologic performance of total hip replacement devices is reviewed. Under the condition of wear as currently experienced at the articulating surfaces of cobalt chromium alloys and ultrahigh molecular weight polyethylene, the amount of metallic products transferred to the tissues is sufficiently low to be well tolerated by the biologic system. Nickel and cobalt ions arc, rapidly transported from the implant site and eliminated in the urine. Chromium is stored in the tissue and eliminated more slowly. The issue of host hypersensitivity to these elements remains of concern. All 3 elements, in ionic form, are known to cause contact dermatitis. Untoward biologic reactions, including hypersensitivity, should be minimized if wear and corrosion phenomena are minimized.

Effect of cefazolin and vancomycin on osteoblasts in vitro

Abstract: The effect of cefazolin and vancomycin on osteoblast-like cells was studied. Cells from the MG-63 human osteosarcoma cell line were grown in antibiotic free media and exposed to concentrations of cefazolin and vancomycin at order of magnitude intervals between 0 and 10,000 microg/ml. For cefazolin, a second interval was performed between 100 and 1000 microg/ml to define toxic levels more accurately. Cell number and 3H-thymidine incorporation at 0, 24, and 72 hours were determined. The results of this study show that local levels of vancomycin of 1000 microg/ml and less have little or no effect on osteoblast replication, and concentrations of 10,000 microg/ml cause cell death. Concentrations of cefazolin of 100 microg/ml and less have little or no effect on osteoblast replication, 200 microg/ml significantly decrease cell replication, and 10,000 microg/ml cause cell death. The authors conclude that vancomycin is less toxic than is cefazolin to osteoblasts at higher concentrations and may be a better antibiotic for local administration in the treatment of similarly sensitive bacterial infections.