Primary cup stability in THA with augmentation of acetabular defect. A comparison of healthy and osteoporotic bone.

BACKGROUND CONTEXT: Reconstruction of acetabular defect has been advocated as standard procedure in total hip arthroplasty. The presence of bony defects at the acetabulum is viewed as a cause of instability and acetabular wall augmentation is often used without proper consideration of surrounding bone density. The initial cup-bone stability is, however, a challenge and a number of studies supported by clinical follow-ups of patients suggested that if the structural graft needs supporting more than 50% of the acetabular component, a reconstruction cage device spanning ilium to ischium should be preferred to protect the graft and provide structural stability. This study aims to (1) investigate the relationship between cup motion and bone density and (2) quantify the re-distribution of stress at the defect site after augmentation. HYPHOTESIS: Paprosky type I or II, acetabular defects, when reconstructed with bone screws supported by bioabsorbable calcified triglyceride bone cement are significantly less effective for osteoporotic bone than healthy bone. MATERIALS AND METHODS: Acetabular wall defects were reconstructed on six cadaveric subjects with bioabsorbable calcified triglyceride bone cement using a re-bar technique. Data of the specimen with higher bone density was used to validate a Finite Element Model. Values of bone apparent density ranging from healthy to osteoporotic were simulated to evaluate (1) the cup motion, through both displacement and rotation, (2) and the von Mises stress distribution. RESULTS: Defect reconstruction with bone screws and bioabsorbable calcified triglyceride bone cement results in a re-distribution of stress at the defect site. For a reduction of 65% in bone density, the cup displacement was similar to a healthy bone for loads not exceeding 300 N, as load progressed up to 1500 N, the reconstructed defect showed increase of 99 µm (128%) in displacement and of 0.08° in rotation angle. CONCLUSIONS: Based on the results, we suggest that an alternative solution to wall defect augmentation with bone screws supported by bioabsorbable calcified triglyceride bone cement, be used for osteoporotic bone. LEVEL OF EVIDENCE: Level IV, experimental and cadaveric study.

Femoral shaft fracture after hip arthroplasty: a system for classification and treatment.

Twenty-one consecutive cases of femoral shaft fracture after hip arthroplasty treated at the University of Illinois affiliated hospitals were reviewed. Adequate follow-up and radiographs were available for 19 patients. The length of follow-up after fracture ranged from 2 to 13 years, with a mean of 3.1 years. The time from index procedure to fracture averaged 2.6 years, with a range of 10 days to 11 years. The primary femoral stem was cemented in 11 hips and cementless in 8 hips. Six patients were treated nonoperatively and 13 operatively. Three had fracture fixation with retention of a well-fixed prosthesis and 10 had prosthetic revision. Cortical allograft was used in 5 cases. Sixteen of the 19 patients returned to their prefracture level of function and ambulation. The factors important to treatment are fracture stability, implant stability, and adequacy of bone stock. A classification system based on these factors and recommendations for treatment are proposed.

Proprioception after arthroplasty: role of the posterior cruciate ligament.

To test the hypothesis that retaining the posterior cruciate ligament during total knee arthroplasty helps preserve the threshold of proprioceptive sensation, a machine was designed that permitted direct measurement of passive angular deflection from a resting point to the threshold of patient perception. Sixty patients with unilateral primary total knee arthroplasties were evaluated; 30 with posterior cruciate ligament retaining prostheses and 30 with posterior cruciate ligament substituting prostheses. All patients had a minimum postoperative followup of 1 year, a good or excellent result as defined by the Hospital for Special Surgery Knee Score, and no evidence of peripheral neuropathy. The gender and age distributions were equivalent between groups. The average threshold of perception for the posterior cruciate ligament retention group was 2.4 degrees. The average threshold of perception for the posterior cruciate ligament substitution group was also 2.4 degrees. Substitution or retention of the posterior cruciate ligament makes no clinical difference in proprioception as measured by threshold testing. This study provides new information for surgeons performing total knee arthroplasty to aid in the decision to retain or substitute the posterior cruciate ligament. Previous proprioception evaluation in patients with posterior cruciate ligament retaining versus posterior cruciate ligament substituting arthroplasties, using different testing methods, has revealed different results.

Treatment of moderate to severe slipped capital femoral epiphysis with extracapsular base-of-neck osteotomy.

Extracapsular base of femoral neck osteotomy was performed in 36 hips with moderate to severe slipped capital femoral epiphysis (SCFE). Follow-up ranged from 2 to 24 years (average 9 years). According to modified Southwick's criteria, 90% of the hips had excellent or good result. There were no cases of avascular necrosis (AVN). Prevention of permanent limb-length discrepancy > 15 mm, as occurs in unilateral cases, warrants close follow-up and contralateral epiphysiodesis when necessary. We highly recommend this osteotomy as a safe and effective way to prevent further slippage and improve hip range of motion (ROM) in severe chronic slips.

Increased superoxide anion production in polymorphonuclear leucocytes on exposure to isobutyl-2-cyanoacrylate.

Alkyl-2-cyanoacrylates have been employed in a variety of surgical procedures, although the pathophysiological basis for their cytotoxicity has not been resolved. Previous reports indicated that leucocytes infiltrate the site of cyanoacrylate application in situ. Consequently, human polymorphonuclear leucocytes were treated with 0-200 mM cyanoacrylate isobutyl-2- and superoxide anion radical production, lactate dehydrogenase release, and intracellular reduced glutathione content were quantitated following this treatment. In addition, some cells were also treated with 0-20 mM ascorbic acid before exposure to the adhesive. Pretreatment with ascorbic acid resulted in a statistically significant decrease in superoxide production (up to 111%), decrease in lactate dehydrogenase release (up to 26.4%) and a like increase in glutathione content (up to 26.6%). These results indicated that the cytotoxic properties of isobutyl-2-cyanoacrylate were diminished in a dose-dependent manner with addition of ascorbic acid, a free radical trapping agent. Moreover, isobutyl-2-cyanoacrylate appeared to increase specifically the production of superoxide anion. These findings suggested that the cytotoxicity of this class of adhesives may be associated with the formation of reactive oxygen intermediates.

Biochemical changes in knee joint articular cartilage after cemented prosthetic hip hemiarthroplasty in dogs.

Biochemical changes in the distal femoral articular cartilage (knee joint) after cemented prosthetic replacement of the femoral head were determined. Femurs from dogs (n = 10) that had undergone cobalt-chromium prosthetic hip hemiarthroplasty (6-8 months postoperatively) were analyzed for articular cartilage lipids in the distal femur. The quantity of phosphatidylserine increased from 0.59 +/- 0.14 mg (uninvolved) to 1.52 +/- 0.23 mg (hemiarthroplasty) lipid phosphorus/100 g tissue, and the quantity of arachidonic acid in the articular cartilage increased from 0.23 +/- 0.07 mg (uninvolved) to 2.07 +/- 0.29 mg/100 g tissue (hemiarthroplasty). Likewise, hydroxyproline content was higher in the recipient femurs (77.4 +/- 1.58 micrograms/mg cartilage) versus uninvolved femurs (71.8 +/- 1.03 micrograms/mg cartilage); the activity of acid phosphatase was greater in the recipient distal femoral cartilage as compared with the uninvolved femur, 0.07 +/- 0.01 and 0.06 +/- 0.02 mol hydrolyzed per kilogram per hour, respectively, and the hexosamine content was lower in the recipient femur knee cartilage versus knee cartilage from uninvolved femurs, 54.5 +/- 1.51 and 63.1 +/- 1.37 micrograms/mg cartilage, respectively. These biochemical changes may suggest degeneration of the knee joint articular cartilage after cemented hip hemiarthroplasty.

Polymorphonuclear leukocyte degranulation with exposure to polymethylmethacrylate nanoparticles.

Polymethylmethacrylate (PMMA) is clinically employed in a wide range of orthopaedic procedures. The etiology of the inflammatory reaction of recipient tissues to PMMA remains unresolved. Classically, polymorphonuclear leukocytes (PMNs) release cytoplasmic lysosomal granules when exposed to a variety of proinflammatory stimuli. Such degranulation contributes, and partially defines, the local tissue reaction to this foreign material. In the present investigation, PMMA particles (50-60 nm) were mixed with human PMNs, and the amount of lactate dehydrogenase, lysozyme, and beta-glucuronidase released from the cells was quantitated. In all cases, a dose-dependent increase in degranulation followed the addition of increasing amounts of PMMA to the PMNs. In addition, the migration of PMNs was diminished in a dose-dependent manner with exposure to increasing amounts of the cement. These results suggested that PMMA stimulates the release of leukocyte lysosomal contents and alters the migration characteristics of these cells in a manner that is consistent with the local inflammatory reaction to this cement.

Healing potential of experimental meniscal tears in the rabbit. Preliminary results.

This study assessed the healing potential of longitudinal or transverse incisions in the peripheral, central, and inner rim regions of rabbit medial menisci. Longitudinal and transverse incisions were made in 48 male New Zealand white rabbits. The incisions were either repaired with sutures or left open. The effect of joint motion on repair was also evaluated. In one group, longitudinal incisions were made in the peripheral, central, and inner rim regions of the meniscus. Some of these incisions were sutured, whereas others were not repaired. In another group, transverse incisions were made in the meniscus, extending from the inner rim to the middle of the meniscus or to the peripheral attachment (radial tear). Again, the lesions were left open or repaired. The effect of joint motion on healing was assessed by immobilizing several knees from each group with Kirschner wires temporarily for ten weeks. Suture of the meniscus incision did not substantially affect the rate of healing. When the healing rates of menisci at the periphery, body, and rim were compared, incisions at the periphery healed significantly better than incisions at the meniscal body and central rim regions. K-wire immobilization did not substantially affect the rate of healing. The difference in healing with regard to the type of incision, either longitudinal or transverse, was not statistically significant.

Clinical and motion studies of the Bateman bipolar prosthesis in osteonecrosis of the hip.

Forty-seven hips in 38 patients with femoral head osteonecrosis were reviewed for a mean follow-up period of 2.6 years. The average preoperative Harris hip score was 24.7; postoperatively, the average score was 84.5. Cineroentgenographic motion studies were carried out on 14 hips and revealed motion at both the inner and outer bearing up to seven years postoperatively. In the unloaded mode, inner- and outer-bearing motion were equal. In the weight-bearing position, inner-bearing motion increased significantly while outer-bearing motion decreased. Only one case of acetabular wear or protrusio was noted.

Bateman hemiarthroplasty component disassembly. A report of three cases of high-density polyethylene failure.

Mechanical failures occurred in three Bateman bipolar hemiarthroplasties in two patients. In all three occurrences, the disassembly of the bipolar prosthesis was caused by fracture of the polyethylene liner of the bipolar acetabular component. This caused the 22-mm head of the femoral component to separate and unlock from the acetabular component. Both patients have functional hips after replacement of the acetabular component with a new "self-centering" type. The mechanical design may predispose this bipolar hemiarthroplasty to disassemble.

Detection of musculoskeletal infection with the indium-III leukocyte scan.

Indium-111-labeled leukocyte scans were performed on 39 patients with suspected musculoskeletal infections to assess the usefulness of this study in detecting bone and joint infections. Results of these scans, as well as results of technetium-99m bone scans, were correlated with the patients' final diagnoses. The indium scan had an overall sensitivity of 77%, a specificity of 69%, and an accuracy of 72%. In 10 patients with a duration of symptoms of six weeks or less, the sensitivity was 100% and the specificity was 75%. In 29 patients with symptoms of greater than six weeks, the sensitivity and specificity were lower at 50% and 71% respectively. Technetium-99m bone scans were performed on 23 patients; sensitivity for infection was 100% while specificity was 60%. Our results suggest that the indium-111 leukocyte scan is a useful adjunct in the diagnosis of acute musculoskeletal infections, but may be inconclusive in chronic infections.

The effect of adjunctive methylmethacrylate on failures of fixation and function in patients with intertrochanteric fractures and osteoporosis.

In a retrospective review of eighty-two intertrochanteric fractures (twenty-nine stable and fifty-three unstable) in seventy-nine elderly, debilitated patients with associated advanced osteoporosis (Grade III or less by the system of Singh et al.), fifty-six were available for follow-up: twenty-eight that had been treated at the University of Illinois with an approximately anatomical reduction and compression-screw fixation and twenty-eight (in twenty-seven patients) that had been treated at the University of Chicago with an approximately anatomical reduction, compression-screw fixation, and adjunctive methylmethacrylate bone cement in the head-neck fragment. Follow-up analysis after an average of thirty-four months for the group that had augmentation with cement and an average of twenty-six months for the uncemented group showed that for the eighteen stable fractures that could be followed the rates of complications of fixation were the same in the two groups, while for the thirty-eight unstable comminuted fractures that were followed the rate of complications of fixation was lower when adjunctive methylmethacrylate cement was used. Among the unstable fractures, one failure (in twenty-one fractures) in the cement-augmented group and ten failures (in seventeen fractures) in the uncemented group were due to failure of fixation (p less than 0.01). For reasons that are not clear, when the thirty-two patients with a healed fracture who could be evaluated for function were rated using the Iowa hip score, the nineteen who were treated with adjunctive cement had significantly lower scores than did the thirteen who were treated without cement (76 +/- 16.5 compared with 92 +/- 12.1, p less than 0.01).

Can carbon fiber implants substitute for collateral ligament?

The biomechanic and histologic changes following replacement of the medial collateral digit of the knee with carbon fiber filament prostheses of varying diameters were studied in young rabbits. Biomechanic testing showed changes with time in the mode of failure and force to failure of the replacements, but the initial differences in the force to failure of the three diameter groups diminished over the 12-week experimental period. Histologic studies with both light and electron microscopy revealed resorption of the carbon fibers and replacement by fibrosed ligaments. There was a correlation between the change in mode of failure and force to failure and increased production, orientation, and organization of new collagen fibrils, as well as simultaneous fragmentation of the carbon fibers.

Early mobilization of rabbit medial collateral ligament repairs: biomechanic and histologic study.

The postoperative management of repaired medial collateral ligaments is controversial. There are proponents for either early mobilization or immobilization. To contribute to an understanding of the issues, 24 adult Dutch rabbits were divided into four groups and a comparative study was made of their incised medial collateral ligaments, contrasting early immobilization with mobilization at three and six weeks. The ligaments were studied histologically and biomechanically. At three weeks, the immobilized ligaments were twice as strong as mobilized ligaments. Histologically, the immobilized ligaments demonstrated more fibroblastic reaction while the mobilized ligaments showed more mature tissue development at the repair site. There were no statistically significant differences between knees mobilized for six weeks and knees immobilized for three weeks and then subsequently mobilized for three weeks. In view of these results, the authors conclude that the deleterious effects of immobilization should be considered when planning postoperative or postinjury treatment of torn medial collateral ligaments.

A comparison between arthrotomy and irrigation and multiple aspirations in the treatment of pyogenic arthritis: a histological study in a rabbit model.

Staphylococcus aureus pyogenic arthritis was produced in a group of eight rabbits. After 24 hours, all rabbits were treated with systemic procaine and benzathine penicillin for five days. Four rabbits were treated with daily aspiration, and four rabbits were treated with arthrotomy and irrigation. A study of the histology of cartilage of the lateral femoral condyle was made in the two groups. Animals treated with aspiration showed a greater degree of thinning of cartilage, acelluiarity, and cloning of chondrocytes than animals treated with arthrotomy and irrigation.

Acrolysis in pachydermoperiostosis. Primary or idiopathic hypertrophic osteoarthropathy.

A 45-year-old black woman was admitted for correction of an equinus deformity of the right lower extremity that resulted from shortening of the Achilles tendon. She exhibited classic findings of pachydermoperiostosis, including clubbing of the digits, periosteal new bone formation, and hypertrophy of skin and its adnexa, associated with several facial acne. In addition, she showed excessive resorption of distal phalanges of the hands and feet, a finding heretofore unreported in pachydermoperiostosis, to our knowledge. Reduced peripheral blood flow has been observed in patients with pachydermoperiostosis; the resorption of distal phalanges observed in our patient may have resulted from this mechanism.

An apparatus for measuring the load-displacement and load-dependent kinematic characteristics of articulating joints-application to the human ankle joint.

An apparatus is described which is capable of measuring the load-displacement characteristics as well as determining the loci of centers of rotation of articulating joints. The apparatus employs a floating head which permits the axis of rotation to coincide with the position of minimum joint resistance, thus eliminating non-physiological rotations at the joint. The coupled loads are also measured, thus providing an accurate description of the joint structural characteristics. Data taken from a freshly amputated human ankle joint is presented.

Subchondral cyst of bone: a case report.

This is a report of a subchondral cyst of the entire fibular head in a 24-year-old woman, and a survey of the literature including pathogenesis, histopathology, and management. Subchondral bone cyst in this location seems not to have been reported previously. The treatment was excision of the head of the fibula.