Showing papers in "Clinical Orthopaedics and Related Research in 1992"

The relationship between stress shielding and bone resorption around total hip stems and the effects of flexible materials

Abstract: Bone resorption around hip stems is a disturbing phenomenon, although its clinical significance and its eventual effects on replacement longevity are as yet uncertain. The relationship between implant flexibility and the extent of bone loss, frequently established in clinical patient series and animal experiments, does suggest that the changes in bone morphology are an effect of stress shielding and a subsequent adaptive remodeling process. This relationship was investigated using strain-adaptive bone-remodeling theory in combination with finite element models to simulate the bone remodeling process. The effects of stem material flexibility, bone flexibility, and bone reactivity on the process and its eventual outcome were studied. Stem flexibility was also related to proximal implant/bone interface stresses. The results sustain the hypothesis that the resorptive processes are an effect of bone adaptation to stress shielding. The effects of stem flexibility are confirmed by the simulation analysis. It was also established that individual differences in bone reactivity and mechanical bone quality (density and stiffness) may account for the individual variations found in patients and animal experiments. Flexible stems reduce stress shielding and bone resorption. However, they increase proximal interface stresses. Hence, the cure against bone resorption they represent may develop into increased loosening rates because of interface debonding and micromotion. The methods presented in this paper can be used to establish optimal stem-design characteristics or check the adequacy of designs in preclinical testing procedures.

Mechanism and clinical significance of wear debris-induced osteolysis

Abstract: Loosening of joint replacement components is often multifactorial. The quality of initial fixation is very important to the outcome of the arthroplasty and is often a factor in short-term and long-term failure. This paper discusses another important factor of implant loosening, namely wear debris induced osteolysis. Macrophages activated by the phagocytosis of particulate wear debris are the key cells in this process, which can potentially occur in any implant system regardless of implant design or fixation mode. This is because each implant system creates wear debris from the articulating surfaces and the interfaces. The clinical consequences of wear debris cover a broad spectrum from radiolucencies to massive osteolysis and implant failure. For this reason, the reduction of wear debris should be a primary goal of orthopedic research in the future.

Preoperative planning for high tibial osteotomy. The effect of lateral tibiofemoral separation and tibiofemoral length.

Abstract: To calculate the tibial wedge size in preoperative planning of high tibial osteotomy, the weight-bearing line (center femoral head to center tibiotalar joint) is first restored to a selected position on the lateral tibial plateau. Ten full-standing roentgenograms were examined and used to derive mat

Elbow subluxation and dislocation. A spectrum of instability.

Abstract: After sequential releases of the ligaments and capsules of 13 fresh autopsy specimen elbows, external rotation and valgus moments with axial forces resulted in posterior dislocations in 12 of the 13 with the anterior medical collateral ligament (AMCL) intact. Kinematic displacements measured with a three-dimensional electromagnetic tracking device showed that dislocation involved posterolateral rotation of 34 degrees-50 degrees and 5 degrees-23 degrees valgus at about 80 degrees flexion. Dislocation is the final of three sequential stages of elbow instability resulting from posterolateral rotation, with soft-tissue disruption progressing from lateral to medial. In each stage, the pathoanatomy correlated with the pattern and degree of instability. Testing for valgus stability of the elbow during simulated active flexion revealed no significant increase (-0.3 degrees-2.4 degrees) in valgus laxity after reduction compared with the intact specimens (p greater than 0.05, beta = 0.1, delta = 2.5 degrees). In no case did the digitized AMCL origin-to-insertion distance increase beyond normal during the dislocation (p less than 0.01). The mechanism of dislocation during a fall on the outstretched hand would involve the body "rotating internally" on the elbow, which experiences an external rotation/valgus moment as it flexes. Posterior dislocations should therefore be reduced in supination. If valgus stability in pronation is demonstrated, the AMCL can be assumed to be intact, and rehabilitation in a hinged cast-brace with the elbow in full pronation can be commenced immediately.

Scapulothoracic motion in normal shoulders and shoulders with glenohumeral instability and impingement syndrome. A study using Moiré topographic analysis.

Abstract: Qualitative visual inspection and manual muscle testing are traditional methods of evaluation that may overlook subtle weakness of the axioscapular musculature. A modification of the standard technique of Moire topographic analysis of spinal deformity was applied to assess axioscapular muscle function in 51 subjects: 22 asymptomatic individuals, 22 with shoulder instability, and seven with impingement syndrome. Static Moire evaluation demonstrated scapulothoracic asymmetry or increased topography in 14% of asymptomatic subjects, compared with 32% and 57% in the instability and impingement groups, respectively. The dynamic Moire test demonstrated an abnormal Moire pattern in 18% of asymptomatic individuals, compared with 64% and 100% in the instability and impingement groups, respectively. Axioscapular muscle dysfunction is common with both instability and impingement syndrome of the shoulder, although it remains to be determined whether this represents a primary or secondary phenomenon.

Producing and avoiding stress shielding. Laboratory and clinical observations of noncemented total hip arthroplasty

Abstract: Experimental canine model studies of stiff versus flexible, fully porous-coated, metallic femoral stems (differing by three- to fivefold in stiffness characteristics) revealed markedly different resorptive bone remodeling patterns. The flexible stem resulted in about 30% more cortical bone retention adjacent to the implant at one-year postimplantation and larger differences in dogs killed two and three years after surgery. Strain-gauge studies confirmed that there are differences in cortical bone strains with the two stem designs, the flexible stem producing a more uniform and more nearly normal strain distribution medially. Differences in cortical bone remodeling were quantified using dual energy X-ray absorptiometry (DEXA). The bone mineral content in femora with the flexible stem decreased less than 20%, compared to normal. At three years postimplantation, the bone mineral content of the femora with the stiff stem was about 50% that of the femora with the flexible stem. Clinically, DEXA revealed that 5%-15% changes in bone mineral density at various periimplant sites were common within the first two years after surgery; these changes were not usually evident roentgenographically. Serial roentgenographically distinct bone resorption was usually associated with bone mineral density changes of 20%-50%. Five- to 13-year roentgenographic follow-up observations of 213 cases with the Anatomic Medullary Locking prosthesis showed that pronounced bone resorption occurred in 33% of patients. Larger stems (greater than 13 mm in diameter) and stems with extensive porous coating had a significantly higher incidence of pronounced bone resorption than smaller stems and those with proximal coating. The stiffness characteristics of the human femur were established as a function of canal size and compared with those of noncemented hip prostheses. Increased mechanical compatibility was found for stems made of titanium alloy and with design features that reduce cross-sectional area and moment of inertia. Clinical data suggest that to reduce the likelihood of pronounced bone resorption, it would be beneficial for the implant to possess a bending stiffness of about one half to one third that of the human femur.

Latissimus dorsi transfer for the treatment of irreparable tears of the rotator cuff

Abstract: Sixteen irreparable, massive rotator cuff tears were treated with latissimus dorsi transfer and reviewed after an average of 33 months. There were no neurovascular complications or infections. Pain relief was satisfactory in 94% of the shoulders at rest and in 81% on exertion. Flexion was 83 degrees preoperatively and 135 degrees postoperatively. The functional value of the shoulder averaged 73% of an age- and gender-adjusted normal score. For the 12 shoulders with a functional subscapularis, it averaged 82%; for those four without a functioning subscapularis, 48%. If the subscapularis was torn and could not be adequately repaired, latissimus dorsi transfer was of no value. In cases with good subscapularis function but irreparable defects in the external rotator tendons, restoration of approximately 80% of normal shoulder function was obtained, indicating that latissimus dorsi transfer is a safe and valuable alternative for the treatment of this specific type of irreparable rotator cuff tear.

Newest knowledge of low back pain : a critical look : Newest knowledge of low back pain

Abstract: Scientific scrutiny of the low back problem demonstrates its socioeconomic importance in most industrialized its socioeconomic importance in most industrialized societies. Natural history studies reveal that the prognosis for the low back pain patient is excellent; for those with sciatica and painful spondylolisthesis it is good. It is even relatively good for those older patients with symptoms of spinal stenosis. Although today there is a better understanding of pain, the pathomechanism of low back pain is unknown

The mechanism of loosening of cemented acetabular components in total hip arthroplasty : analysis of specimens retrieved at autopsy

Abstract: Late aseptic loosening of cemented acetabular components is governed by the progressive, three-dimensional resorption of the bone immediately adjacent to the cement mantle. This process begins circumferentially at the intraarticular margin and progresses toward the dome of the implant. Evidence of bone resorption at the cement-bone interface was present even in the most well-fixed implants before the appearance of lucent lines on standard roentgenographic views. The mechanical stability of the implant was determined by the three-dimensional extent of bone resorption and membrane formation at the cement-bone interface. The leading edge of the membrane is a transition zone from regions of membrane interposition between the cement and the bone to regions of intimate cement-bone contact. Histologic analysis revealed that progressive bone resorption is fueled by small particles of high density polyethylene (HDP) migrating along the cement-bone interface and bone resorption occurs as a result of the macrophage inflammatory response to the particulate HDP. Evidence in support of a mechanical basis for failure of fixation was lacking. The mechanism of late aseptic loosening of a cemented acetabular component is therefore biologic in nature, not mechanical. This is exactly opposite to the mechanism of loosening on the femoral side of a cemented total hip replacement, which is mechanical in nature.

Development of a surgical robot for cementless total hip arthroplasty.

Abstract: The long-term success of cementless total hip arthroplasty (THA) may depend on bone ingrowth into the porous-fixation surfaces of the implant. The ingrowth process is facilitated when the surgeon achieves a satisfactory fit for the prosthesis. Clinically or roentgenographically visible failure and p

Mechanical axis deviation of the lower limbs. Preoperative planning of uniapical angular deformities of the tibia or femur.

Abstract: Angular deformities of the tibia or femur in the frontal plane lead to mechanical axis deviation of the lower limb and malorientation of the joints above and below the level of deformity. Accurate correction of the malalignment and of the joint orientation is important for function and to prevent joint degeneration. An accurate yet simple method to determine the apex of deformity and the type of correction required is based on the joint reference lines of the hip, knee, and ankle, and the individual mechanical axis lines of each bone segment. If the osteotomy is performed at the level of the apex of the deformity, then the only correction needed is angulation. If the osteotomy is performed at a level proximal or distal to the apex, then translation in addition to angulation is necessary to accurately correct the deformity.

Articular geometry of the glenohumeral joint.

Abstract: Little quantitative data exists defining the true shape of the humeral head and glenoid articular surfaces. This study uses a precise stereophotogrammetry (SPG) technique and provides highly accurate quantitative results for determining the three-dimensional geometry of glenohumeral joint articular surfaces, including their "sphericity", surface areas, cartilage thickness, and the difference in these quantities between the genders. Results indicate that glenohumeral joint surfaces may be approximated by a section of a sphere with small deviations from sphericity of less than 1% of the radius. Furthermore, results indicate that mating humeral head and glenoid articular surfaces are quite congruent and have radii within 2 mm in 88% of cases, and within 3 mm in all cases measured. The lack of anatomic stability of this joint is therefore not attributable to the relative shallowness or lack of congruence of the joint but rather to the small surface area of the glenoid which does not enclose the humeral head. Cartilage thickness results may partially explain perceptions of glenohumeral incongruity obtained from roentgenographic measurements where the glenoid appears flatter than the corresponding humeral head. Only when the actual articular cartilage surfaces are analyzed is it determined that the actual articulating surfaces do conform.

Determinants of stress shielding: design versus materials versus interface

Abstract: Experimental studies of cementless porous-coated total hip arthroplasty indicate that a critical design variable for femoral remodeling is stem stiffness. In the long term (two years) in the canine model, other variables, including the presence, type, and placement of the porous coating, did not significantly affect the pattern of bone remodeling when tested with metallic stems. The basic pattern of bone remodeling was characterized by proximal cortical atrophy, and distal cortical and medullary bone hypertrophy. In the short term (six months), the use of low-stiffness stems altered this pattern, leading to reduced proximal bone loss, increased proximal medullary bone hypertrophy, and no distal cortical hypertrophy, suggesting that stem stiffness had a profound effect on stress shielding.

The treatment of infected nonunions and segmental defects of the tibia by the methods of Ilizarov.

Abstract: Circular external fixation using the Ilizarov apparatus combined with internal bone transport or compression-distraction techniques were used to treat 28 patients with infected nonunions or segmental bone loss of the tibia. There were 22 males and six females with an average age of 34 years (range, 17-58 years). Six of 28 patients had infected tibial nonunions associated with hemicircumferential bone loss. These tibiae were treated by anterior hemicircumferential corticotomy and partial bone fragment internal transport. Fifteen of the remaining 22 patients had an average of 4 cm of segmental bone loss (range, 2-7 cm). Seven patients without shortening or defect had infected nonunions associated with extensive diaphyseal sequestrae. These nonunions were treated by en bloc resection of the diaphyseal shaft and internal bone transport. All patients healed their infected extremities without the addition of cancellous bone graft, microvascular fibular, or soft-tissue grafting. Preoperative shortening was present in 13 of 28 patients. Regenerate new bone formation averaged 6 cm (range, 1.5-22 cm). Postoperative antibiotics were not administered in 21 of 28 patients. In seven patients, antibiotics were given for ten days after en bloc resection of the diaphyseal sequestrae. Equal limb length was maintained in 21 extremities, within 1 cm in five tibiae and less than 3 cm in two tibiae. Functional results were good to excellent in 21, fair in six, and poor in one. The application of Ilizarov techniques to diaphyseal infected nonunions and segmental defects is very encouraging. It may prove to be an excellent technique for future management of resistant diaphyseal infections of bone.

Newest knowledge of low back pain. A critical look.

Abstract: Scientific scrutiny of the low back problem demonstrates its socioeconomic importance in most industrialized societies. Natural history studies reveal that the prognosis for the low back pain patient is excellent; for those with sciatica and painful spondylolisthesis it is good. It is even relatively good for those older patients with symptoms of spinal stenosis. Although today there is a better understanding of pain, the pathomechanism of low back pain is unknown. However, for patients with sciatica, spondylolisthesis, and spinal stenosis, physicians are beginning to get a better perception of what causes the pain. Psychosocial factors, including insurance benefits, have been demonstrated to be more important than biomechanical workload not only for acute but also for chronic low back pain patients who are unable to work. Orthopedic surgeons must recognize this fact when contemplating operations for patients with ill-defined back syndromes. Rarely are diagnoses scientifically valid, nor is the effectiveness of surgery proven by acceptable clinical trials.

Quantification of implant micromotion, strain shielding, and bone resorption with porous-coated anatomic medullary locking femoral prostheses.

Abstract: Fourteen femora containing porous-coated anatomic medullary locking (AML) femoral prostheses were retrieved from 12 patients at autopsy. Clinical roentgenograms in 13 femora showed bone remodeling changes, indicating that the implants were fixed by osseointegration. Under simulated physiologic loading, micromotion between the implant and the bone was measured using electrical displacement transducers connected to the implant and to the adjacent cortex. The micromotion between the implants at the areas of porous coating and the adjacent cortex in the one case of failed bone ingrowth measured 150 microns. Maximum relative motion between the cortex and the implant in the areas of porous coating for the 13 cases showing signs of bone ingrowth was 40 microns, and this was completely elastic relative displacement. With all implants, the micromotion between the cortex and the stem was always greatest over the uncoated portion of the stem. Four of the implants were proximally porous coated. With these, the micromotion was greater over the uncoated areas than with more extensively coated stems and was always greatest at the uncoated tip of the prosthesis. The amount of micromotion was directly related to the extent of porous coating on the implant. Maximum tip motion for the proximally coated implants was 210 micra, whereas for the fully porous-coated implants, it was 40 microns. In nine of the autopsies, the contralateral normal femur was obtained in addition to the femur containing the AML (the in vivo remodeled femur). These were used for comparative studies of strain shielding and femoral remodeling. Cortical strains were measured in the in vivo remodeled femora and were compared with measurements made in the contralateral normal femora before and following implantation of a stem identical to that present on the clinically treated side. The data showed major strain reductions in all the postmortem implanted normal femora. Comparison of the strain data from the postmortem implanted normal femora with those from the in vivo remodeled femora clearly indicated that extensive bone remodeling did not result in restoration of cortical strain levels anywhere near normal. Strain shielding continued to exist in all of the remodeled specimens, even up to 7.5 years after surgery. This strain shielding was associated with bone remodeling changes that resulted in regional reductions in bone mineral content that ranged from 7% to 78%. These observations are unique, important, and valuable in defining the in vivo function and clinical behavior of this type of porous-coated femoral component.

Scapulothoracic motion in normal shoulders and shoulders with glenohumeral instability and impingement syndrome

Abstract: Qualitative visual inspection and manual muscle testing are traditional methods of evaluation that may overlook subtle weakness of the axioscapular musculature. A modification of the standard technique of Moiré topographic analysis of spinal deformity was applied to assess axioscapular muscle function in 51 subjects: 22 asymptomatic individuals, 22 with shoulder instability, and seven with impingement syndrome. Static Moiré evaluation demonstrated scapulothoracic asymmetry or increased topography in 14% of asymptomatic subjects, compared with 32% and 57% in the instability and impingement groups, respectively. The dynamic Moiré test demonstrated an abnormal Moiré pattern in 18% of asymptomatic individuals, compared with 64% and 100% in the instability and impingement groups, respectively. Axioscapular muscle dysfunction is common with both instability and impingement syndrome of the shoulder, although it remains to be determined whether this represents a primary or secondary phenomenon.

Transtrochanteric anterior rotational osteotomy for idiopathic and steroid-induced necrosis of the femoral head. Indications and long-term results.

Abstract: From 1972 until 1988, transtrochanteric rotational osteotomy was used to treat 474 hips in 378 patients with idiopathic and steroid-induced osteonecrosis of the femoral head. Two hundred twenty-nine of 295 hips with anterior rotation and follow-up periods ranging from three to 16 years had excellent surgical results (success rate, 78%). Outcome was chiefly dependent on the ratio of transposed intact posterior articular surface to the acetabular weight-bearing area after osteotomy. This relationship suggested that the transposed intact area should occupy more than 36% of the acetabular weight-bearing area by adequate rotation and intentional varus position in addition to rotation, especially for extensive lesions. Salvage operations, such as total hip arthroplasty, were performed on 18 hips, of which ten hips were cases of either relative indication for extensive lesions in young patients or other misindications for rotational osteotomy. Four hips sustained neck fracture, including three hips after 180 degrees of posterior rotation; two hips were complicated with avascular necrosis, and another two hips developed osteoarthrosis. Histologically, femoral heads with osteoarthrosis removed at the time of salvage operation showed complete healing of the necrotic lesion. The overall findings indicate that healing of the necrotic lesion of the femoral head may be brought about by rotational osteotomy if it spares the vulnerable site from the brunt of mechanical stress.

Tibial tunnel placement in anterior cruciate ligament reconstructions and graft impingement.

Abstract: Fifty-six anterior cruciate ligament (ACL) reconstructions had a magnetic resonance scan of the ACL graft six months after operation. The impingement-free grafts (n = 26) had a low magnetic resonance signal from origin to insertion. Impinged grafts (n = 30) had an increased magnetic resonance signal confined to the distal two thirds of the graft. The location of the tibial tunnel (TT) was determined from a lateral roentgenogram. Positioning the center of the TT 12-23 mm from the anterior edge of the tibia consistently produced graft impingement and flexion contractures. Roof impingement was avoided and hyperextension was regained when the TT was centered more posteriorly within a 6-mm impingement-free zone (22-28 mm from the anterior edge of the tibia). Stability and knee extension were significantly better when the center of the TT was 2-3 mm posterior to the center of the normal ACL insertion.

Postoperative posterior spinal wound infections.

Abstract: The incidence of postoperative spinal infections increases with the complexity of the procedure. Diskectomy is associated with less than a 1% risk of infection; spinal fusion without instrumentation is associated with a 1%-5% risk; and fusion with instrumentation may be associated with a risk of 6% or more. Twenty-two postoperative posterior spinal infections that occurred during a three-year period were reviewed for this report. Staphylococcus aureus was the most frequent organism cultured (more than 50% of the cases). Other recurring organisms were Staphylococcus epidermis, Peptococcus, Enterobacter cloacae, and Bacteroides. Many patients had multiple organisms. Risk factors appeared to include advanced age, prolonged hospital bed rest, obesity, diabetes, immunosuppression, and infection at remote sites. Operative factors included prolonged surgery (greater than five hours), high volume of personnel moving through the operating room, and instrumentation. Postoperative contamination may occur and may be related to prolonged postoperative bed rest, skin maceration (thoracolumbosacral orthoses), and drainage tubes exiting distally from lumbar wounds (toward the rectum). Effective treatment includes early diagnosis, surgical debridement and irrigation, and parenteral antibiotics. Superficial infections were treated successfully with wound closure over outflow tubes, and deep infections with inflow-outflow systems. Maintaining the instrumentation in place was possible in most cases. Parenteral antibiotics were maintained for six weeks in every case.

In vitro and in vivo evaluation of antibiotic diffusion from antibiotic-impregnated polymethylmethacrylate beads.

Abstract: The elution of antibiotics from antibiotic-impregnated polymethylmethacrylate (PMMA) beads was measured in mongrel dogs. The antibiotics, used in mixture with Simplex cement, included cefazolin (Ancef; 4.5 g/40 g cement powder), ciprofloxacin (Cipro; 6 g/40 g powder), clindamycin (Cleocin; 6 g/40 g powder), ticarcillin (Ticar; 12 g/40 g powder), tobramycin (Nebcin; 9.8 g/40 g powder), and vancomycin (Vancocin; 4 g/40 g powder). After a pneumatic drill was used to dredge a trough in the tibia, five beads were implanted. During the next 28 days, seroma samples and serum samples were taken for antibiotic measurements. On Day 28, the dogs were killed, beads removed, and the seroma, serum, bone, and granulation tissue sampled. The results of the study showed that clindamycin, vancomycin, and tobramycin exhibited good elution characteristics and had consistently high levels in bone and granulation tissue.

The pericyte as a possible osteoblast progenitor cell.

Abstract: Bovine capillary and microvessel pericytes were grown in monolayer in standard tissue culture medium supplemented with 10% newborn calf serum at various oxygen tensions for up to ten weeks. The pericytes synthesized alkaline phosphatase and formed colonies that mineralized. Energy dispersive X-ray spectrometry revealed the presence of calcium and phosphate, showed positive staining for collagen and glycosaminoglycan, and, most importantly, demonstrated the synthesis of osteocalcin. Cell proliferation, hydroxyproline production, and alkaline phosphatase synthesis were greatest in 3% oxygen, whereas osteocalcin production was least in 3% oxygen. These findings demonstrate that the capillary or microvessel pericyte exhibits phenotypic expressions in vitro that are similar to that of in vitro bone cells, and these expressions may be somewhat oxygen dependent. It is suggested from these findings that the capillary or microvessel pericyte may be an osteoblast precursor cell.

Fluoroscopic comparison of kinematic patterns in massive rotator cuff tears. A suspension bridge model.

Abstract: Twelve shoulders with known massive rotator cuff tears were imaged fluoroscopically. The observed kinematic patterns were correlated with the known locations of the rotator cuff tears. Three kinematic patterns emerged: Type I, stable fulcrum kinematics associated with tears of the superior rotator cuff (supraspinatus and a portion of the infraspinatus); Type II, unstable fulcrum kinematics associated with tears that involved virtually all of the superior and posterior rotator cuff; and Type III, captured fulcrum kinematics associated with massive tears that involved the supraspinatus, a major portion of the posterior rotator cuff, and a major portion of the subscapularis. In Type III, an "awning effect" of the acromion was observed to influence active motion. Based on the recorded kinematic patterns, a biomechanical model was developed comparing the rotator cuff tear to a suspension bridge (loaded cable). A biomechanical analysis of forces acting on the rotator cuff according to this model yielded data that supported the contention that certain rotator cuff tears in older individuals may be adequately treated with debridement and decompression, without repair.

The natural course of lumbar spinal stenosis.

Abstract: The course of 32 untreated patients with spinal stenosis was studied. The mean patient age was 60 years, and the mean period of observation was 49 months. About 75% of the patients had spinal claudication. In the follow-up survey, the same number of patients had claudication, but the symptoms were milder. In estimation by visual analog scale, symptoms in 70% of the cases were unchanged, 15% showed improvement, and 15% worsened. No proof of severe deterioration was found after four years, and expectant observation may be an alternative to surgical treatment.

The modified Insall-Salvati ratio for assessment of patellar height.

Abstract: The Insall-Salvati ratio for the assessment of patellar height was the first widely used index to be relatively independent of knee flexion. Despite the subsequent publication of other indices, it remains the most widely used index. The Insall-Salvati ratio nevertheless has drawbacks, one of which has received little attention: the ratio lacks sensitivity to patellar morphology. Unusual patellar shapes can lead to misleading values of the Install-Salvati ratio. In particular, the authors have found a significant number of inaccurate readings for patellar height in patients whose patella exhibits a long distal (nonarticulating) facet. A modified Insall-Salvati ratio is described which, when applied in conjunction with the traditional ratio, significantly reduces these errors. The cutoff point between normal and alta for this modified Insall-Salvati ratio is 2. One half of the cases of patella alta in this study were missed by the traditional ratio, yet identified by the modified index.

A ten- to 15-year follow-up observation of high tibial osteotomy in medial compartment osteoarthrosis.

Abstract: High tibial osteotomy (HTO) was performed on 86 medially osteoarthritic knees in 78 patients. Twelve patients died during the follow-up period. Fifty-six knees of 51 patients were evaluated twice postoperatively: once at six years after surgery and again after ten to 15 years. Results were satisfactory in 88% of the knees at the six-year follow-up evaluation and in 63% at the post-ten-year follow-up evaluation. Ten-year follow-up results significantly deteriorated. The femorotibial angle (FTA) at the time of bone union after HTO was a significant factor that contributed to the ten-year results. In patients maintaining excellent improvement of knee function at the post-ten-year follow-up evaluation, the mean FTA at one year after surgery was 165 degrees; this value was constant through ten years after HTO. An FTA of 164 degrees-168 degrees should be attained to ensure favorable long-term results in HTO.

Anatomic and technical considerations of pedicle screw fixation : Avoidance of complications in spine surgery

Abstract: Pedicle screw systems provide significant and, in many cases, improved and previously unattainable spinal fixation. However, pedicle screw systems represent difficult surgical techniques involving several potential problems and complications. Only by detailed knowledge of the anatomy of the spine, with a clear understanding of the pedicle screw systems implementation, can the risks of complications be minimized

C-reactive protein (CRP) levels after elective orthopedic surgery.

Abstract: The levels of C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were determined by serial measurements after four types of uncomplicated elective orthopedic surgery. The type of operations chosen for this study were total hip arthroplasty (primary, n = 109; and revisions caused by as

Anatomic and technical considerations of pedicle screw fixation.

Abstract: Pedicle screw systems provide significant and, in many cases, improved and previously unattainable spinal fixation. However, pedicle screw systems represent difficult surgical techniques involving several potential problems and complications. Only by detailed knowledge of the anatomy of the spine, with a clear understanding of the pedicle screw systems implementation, can the risks of complications be minimized.

Structure, expression, and regulation of the major noncollagenous matrix proteins of bone.

Abstract: The noncollagenous proteins (NCPs) that predominate the bone matrix have recently been the focus of intense investigation because of their potential influence on cell attachment, Ca2+ and hydroxyapatite binding, and the mineralization of bone tissue. With the advent of molecular biology, all of the