Showing papers in "Clinical Orthopaedics and Related Research in 1995"

The problem is osteolysis

Abstract: Recent studies have generated considerable information that reveals substantial support for major change in the understanding of total hip arthroplasty and its current state. Although some of these observations appear unrelated at first glance, they can be drawn together to support the thesis that osteolysis is the dominant problem in total hip arthroplasty. These observations are as follows: (1) Five-year followup data are required for a minimum assessment of a new concept in total hip design and material because osteolysis is uncommon before that time. (2) Excellent fixation can be achieved on the femoral side with good cementing and good cementless techniques. Thus, femoral component loosening is less of an issue currently. (3) Many acetabular components become loose because of the ingress of particulate debris that leads to linear bone loss at the interface with the pelvis, a process that is biologically akin to the more florid forms of osteolysis. Thus, much acetabular component loosening represents a form of osteolysis. (4) Many cementless femoral reconstructions have developed a high incidence of femoral osteolysis. (5) Many cementless sockets have developed a high incidence of pelvic osteolysis. Taken in conjunction, these observations suggest that periprosthetic osteolysis is the leading problem in contemporary total hip replacement.

Molecular biology of matrix vesicles.

Abstract: Matrix vesicles are extracellular 100-nanometer-diameter membrane-invested particles selectively located within the matrix of bone, cartilage, and predentin. They serve as the initial site of calcification in all skeletal tissues. Matrix vesicle biogenesis occurs by polarized budding and pinching off of vesicles from specific regions of the outer plasma membrane of chondrocytes, osteoblasts, and odontoblasts. Seeding of selected areas of matrix with matrix vesicles explains the localized distribution of subsequent zones of mineralization. Matrix vesicle biogenesis in the growth plate is linked to the chondrocyte cell cycle and reflects a stage in programmed cell death (apoptosis). Generation of initial hydroxyapatite mineral crystals occurs within the matrix vesicle membrane during Phase 1 of biologic mineralization. Phase 1 is controlled by phosphatases (including alkaline phosphatase) and Ca-binding molecules with which the matrix vesicles are well endowed. Phase 2 of biologic mineralization begins with breakdown of matrix vesicle membranes, exposing preformed hydroxyapatite to the extracellular fluid after which mineral crystal proliferation is governed by extracellular conditions. Phase 1 and Phase 2 of mineralization are under cellular control. Phase 1 is initiated by cells generating calcifiable matrix vesicles and releasing them into sites of intended calcification. Phase 2 is controlled by cells regulating extracellular ionic conditions and matrix composition.

Chronic Achilles tendinopathy. A survey of surgical and histopathologic findings

Abstract: The surgical findings and the histopathology are reported for 163 patients (134 males, 29 females; mean age, 38 years; range, 13-72 years; 75% athletes) with chronic Achilles tendinopathy. Biopsy specimens from symptomatic (155 cases) and nonsymptomatic (90 cases) parts of the tendon and from the paratenon (97 cases) were obtained. Surgical reports were reviewed and histopathology was evaluated according to a standardized protocol. Eighteen tendons also were analyzed by immunofluorescence for fibrinogen, immunoglobulins, and complement. Degenerative changes (tendinosis) characterized by abnormal fiber structure, focal hypercellularity, and vascular proliferation were noted in 90% of biopsy specimens from symptomatic parts of the tendons and, to a lesser degree, in 20% from nonsymptomatic parts. Fibrinogen could be identified in most lesion biopsy specimens. Partial tendon ruptures were present in 19% of the patients and always occurred in areas afflicted with tendinosis. The paratenon was mostly normal or revealed only slight changes. Increasing age and male gender were associated with more pronounced histopathologic changes. Tendinosis, sometimes complicated by partial rupture, appears to be the major lesion in chronic Achilles tendinopathy; the paratenon is rarely involved. Important features are a lack of inflammatory cells and a poor healing response.

The anteroposterior axis for femoral rotational alignment in valgus total knee arthroplasty.

Abstract: This study evaluated a technique using the anteroposterior axis of the distal femur, rather than the transepicondylar or posterior femoral condylar axis, to establish rotational alignment of the femoral component in valgus knees. The anteroposterior axis of the distal femur was defined by a line through the deepest part of the patellar groove anteriorly and the center of the intercondylar notch posteriorly. Total knee arthroplasty was done in 46 valgus knees between 1980 and 1986 using the posterior femoral condyles as landmarks for rotational alignment. From January 1986 through January 1992 total knee arthroplasty was done in 107 valgus knees using the anteroposterior axis for rotational alignment of the femoral component. In the group of knees using the posterior condylar axis, medial tibial tubercle transfer was needed intra-operatively in 8 knees to prevent lateral dislocation of the patella. In the first 2 postoperative years, 4 knees had recurrent patellar dislocation or subluxation that required surgical correction. In the group of knees using the anteroposterior axis, patellar tracking problems that required realignment were significantly reduced. One knee required medial tibial tubercle transfer to correct a Q angle > 20 degrees. In the remaining knees, the Q angle was < 10 degrees, and patellar tracking was acceptable. Two years after surgery, no knees had patellar instability.

The origin of submicron polyethylene wear debris in total hip arthroplasty.

Abstract: The microscopic morphology of worn polyethylene surfaces was compared with that of the associated polyethylene particles for acetabular cups tested in a wear simulator and for cups worn in vivo, using scanning electron microscopy. In the absence of significant third-body abrasive damage, the articulation of the ball in the cup produced a visually polished surface on the polyethylene. On a micron scale, the morphology of the worn polyethylene from in vitro and in vivo wear included nodules and fibrils consistent with adhesive, abrasive, and microfatigue wear mechanisms. Larger wear features, such as deep scratches or pits measuring in 10s of microns, that were seen in the in vivo cups were attributed to third-body wear. The polyethylene particles isolated from the serum lubricants of the wear tests and from the periprosthetic tissues were primarily submicron in size, were either rounded or elongated, and were consistent with the submicron wear features seen on the cup surfaces. It is the submicron particles that are associated with inflammatory periprosthetic bone loss in total hip replacement. Although the mean dimensions of the particles generated in vitro were slightly smaller than those of the in vivo particles, the overall morphologies were very comparable, suggesting that the same lubrication and wear processes were acting in the simulator as in vivo.

Collagen in tendon, ligament, and bone healing. A current review.

Abstract: Cells that produce a particular type of collagen under normal physiologic circumstances can be induced by certain local triggers to change the amount and type of collagen synthesized. This has become most apparent during bone, tendon, and ligament healing, where cells that once produced the collagen of normal intact tissue are induced to synthesize different types of collagen at the repair site of injured tissue. For example, Type III collagen, not a major component of the extracellular matrix in normal tendons, is believed to be of great advantage during the healing process because of its ability to form rapid crosslinks and precariously stabilize the repair site. Although much is known about the gross histologic changes occurring during tissue healing, little is known about the specific role of the individual collagen types or what influences their development. This review addresses the role of collagen in normal and healing bone, tendon, and ligament. Much experimental effort is needed to uncover the distribution and function of the collagen types within connective tissue elements and the effect of growth factors on the phenotype of collagen produced in these tissue, with the ultimate goal of developing clinical manipulations that take advantage of the unique properties of each type of collagen.

Acetabular labrum tears. Diagnosis and treatment.

Abstract: An acetabular labrum tear was diagnosed and treated in 56 hips in 55 patients. Mechanical hip pain after a relatively minor injury with an associated click characterized the history. The tear of the labrum was shown with arthrography in 88% of the patients. Overall, 89% of the patients were improved by the diagnosis and treatment of an acetabular labrum tear: all 7 patients treated nonsurgically and 42 of 46 patients treated surgically. In recent years, it has been possible to arthroscopically confirm the diagnosis and treat some of these patients.

Radiographic analysis of tibial fracture malalignment following intramedullary nailing.

Abstract: Intramedullary nailing of the tibia was performed on 145 tibiae (137 patients) for fracture or nonunion from 1985 to 1992. There were 133 cases available for radiographic analysis of postoperative tibial alignment. Of the 133 nailings, 16 (12%) were malaligned (12 acute fractures and 4 nonunion-malunions). Malalignment was defined as 5 degrees angulatory deformity in any plane. Malalignment was seen in 58% of proximal third fractures, 7% of middle third fractures, and 8% of distal third fractures. Of the malaligned fractures, 83% were either segmental or comminuted. Thirteen percent of the reamed tibiae were malaligned as compared with 9% of the unreamed tibiae. There was no relationship between nail insertion site and degree of angulation. The medial entrance angle averaged 9.5 degrees and contributed to a valgus deformity in 4 proximal third tibial fractures. The average anterior bow deformity of 5 proximal third fractures was 7 degrees (range, 5 degrees-12 degrees). Careful attention to operative technique and entrance angle, particularly with proximal third or comminuted fractures, is recommended to prevent angular deformity and malunion after tibial nailing. Proximal third tibial fractures may require a neutral or slightly lateral entrance angle to ensure a more anatomic reduction and centromedullary nail orientation to offset the tendency for valgus angulation.

Computer-Integrated Surgery: Technology and Clinical Applications

Abstract: From the Publisher: "New technologies such as medical imaging, surgical navigation, robotics, virtual reality, and surgical simulation may soon influence the way we design, plan, simulate, and execute surgical procedures. Successful clinical introduction of some of these technologies has emerged as a fast growing field of research and development. This book reflects the current state of the art in computer integrated surgery, providing engineers, scientists, and clinicians with an invaluable reference source on the subject." -- Dr. Lutz-P. Nolte, Head of the Orthopaedic Biomechanics Division, M.E. Muller Institute for Biomechanics, University of Bern, Switzerland In Computer-Integrated Surgery leading researchers and clinical practitioners describe the exciting new partnership that is being forged between surgeons and machines such as computers and robots, enabling them to perform certain skilled tasks better than either can do alone. The 19 chapters in part I, Technology, explore the components -- registration, basic tools for surgical planning, human-machine interfaces, robotic manipulators, safety -- that are the basis of computer-integrated surgery. These chapters provide essential background material needed to get up to speed on current work as well as a ready reference for those who are already active in the field. The 39 chapters in part II, Applications, cover eight clinical areas -- neurosurgery, orthopedics, eye surgery, dentistry, minimal access surgery, ENT surgery, craniofacial surgery, and radiotherapy -- with a concluding chapter on the high-tech operating room. Each section contains a brief introduction as well as at least one "requirements and opportunities" chapter written by a leading clinician in the area under discussion.

The role of prostaglandins in the regulation of bone metabolism

Abstract: Prostaglandins are likely to play an important role in the physiologic and pathologic responses of skeletal tissue. They are potent agonists that can stimulate and inhibit bone resorption and formation. In vivo, the major effect of exogenous prostaglandins, particularly prostaglandin E2, is to stimulate resorption and formation. These effects appear to involve replication and differentiation of osteoclast and osteoblast precursors, and to be mediated at least in part by cyclic 3' 5' adenosine monophosphate. Prostaglandins can inhibit the activity of isolated osteoclasts, probably also by a cyclic 3' 5' adenosine monophosphate-mediated mechanism. Inhibition of collagen synthesis can be seen in cell and organ cultures and appears to be caused by a receptor selective for prostaglandins of the F series and to involve activation of protein kinase C. Prostaglandin production by bone cells is regulated highly by mechanical forces, cytokines, growth factors, and systemic hormones. Prostaglandins also can amplify their own production. Regulation is associated with marked changes in the newly described "inducible" prostaglandin G/H synthase with less effect on the constitutive enzyme. Prostaglandins also may play a role in postmenopausal bone loss because estrogen deficiency, which increases bone turnover, can increase prostaglandin production in bone.

Ambulatory ability after hip fracture. A prospective study in geriatric patients.

Abstract: Three hundred thirty-six community-dwelling, previously ambulatory, geriatric patients with hip fracture were observed prospectively to determine ambulatory ability at a minimum followup of 1 year. One hundred thirty-seven (41%) patients maintained their prefracture ambulatory ability at a minimum followup of 1 year; 134 (40%) patients remained ambulatory but became more dependent on assistive devices; 39 (12%) previous community ambulators became household ambulators, and 26 (8%) patients became nonfunctional ambulators. Analysis was performed to determine which pre- and postinjury factors were predictive of failure to recover ambulatory capacity 1 year after fracture. Potential predictor variables analyzed included age, gender, number of comorbid conditions, prefracture ambulatory ability, prefracture living situation, fracture type, American Society of Anesthesiologists rating of operative risk, type of surgery, and number of postoperative complications. Multiple logistic regression analysis identified significant contributions of age, prefracture ambulatory ability, American Society of Anesthesiologists rating of operative risk, and fracture type to ambulatory recovery.

Treatment of Infected Total Knee Arthroplasty Using an Articulating Spacer

Abstract: Twenty-six patients with late infected total knee arthroplasties were treated by debridement and removal of components and all cement, preserving collateral ligaments. At time of debridement, an articulating spacer was fashioned to allow partial weightbearing and knee range of motion (ROM) during rehabilitation. This spacer was implanted using antibiotic-impregnated bone cement. For this purpose, 4.8 g of powdered tobramycin was mixed with each 40-g batch of Simplex cement. Cement was applied early to the components, but applied late to the femur, tibia, and patella to allow molding to the defects and bone without adherence to bone. Patients received tailored intravenous antibiotic therapy for 6 weeks in addition to this antibiotic-impregnated cement for treatment of a variety of gram positive and gram negative organisms. All patients had cemented revision total knee arthroplasty using antibiotic-impregnated cement with standard cementing techniques used. All patients but 1 had reimplantation; this patient died of unrelated causes before revision. Range of motion before revision was 10 degrees to 95 degrees. Followup averaged 30 months (range, 13-70 months). The average Modified Hospital for Special Surgery Knee Score after revision was 87 points (range, 53-100 points), with 92% good to excellent results. Range of motion after reimplantation was 5 degrees to 106 degrees. There have been no recurrences of infection. Use of an articulating spacer to treat infected total knee arthroplasty improves ultimate ROM and soft tissue health and significantly decreases the risk of reinfection.

Determinants of Reduced Survival Following Hip Fractures in Men

Abstract: To assess determinants of poor survival after hip fractures in men, a population-based cohort study was conducted among 131 men in Rochester, MN, who had their first hip fracture during the period from 1978 to 1989, and an equal number of age-matched control men from the community. One hundred nine patients with fractures died during 373 person-years of followup, but only 75 control men died during 742 person-years of observation. The risk of dying increased with the level of comorbidity among hip fracture cases (hazard ratio 3.2; 95% confidence interval, 1.2-8.2), as well as with age (hazard ratio, 1.4 per 10-year increase; 95% confidence ratio, 1.1-1.8) and mental confusion during hospitalization (hazard ratio, 4.2; 95% confidence interval, 2.5-6.9). Discharge to a nursing home and low activity status also were predictors of death in the univariate analysis. Excess mortality among men with hip fractures can be explained best by interaction of the fracture with serious underlying medical conditions.

Dynamic support of the human longitudinal arch. A biomechanical evaluation.

Abstract: This study was designed to evaluate the dynamic support provided to the human longitudinal arch by the leg muscles active in the stance phase of gait and by the plantar aponeurosis. Ten fresh adult cadaveric specimens were mounted in a materials testing machine. The tendons of the posterior tibialis, flexor digitorum longus, flexor hallucis longus, peroneus longus, peroneus brevis, and Achilles tendon were attached to force transducers. Plantar loads of 0, 350 and 700 N were applied, and the tendons were tensioned individually. The Achilles tendon was tensioned an amount equal to the plantar load; the posterior tibialis, flexor digitorum longus, flexor hallucis longus, peroneus longus, and peroneus brevis were tensioned a fractional amount (depending on the proportion of the cross-sectional area to the gastrocsoleus complex). The angular relationships between the first metatarsal, navicular, and talus were recorded using a 3-dimensional movement analysis system. An additional series of measurements was obtained by positioning the ankle plantarflexed 10 degrees under a plantar load of 350 N. Dorsiflexing the toes with the ankle in a neutral position and loading the foot to 350 N and 700 N permitted an evaluation of the effect of the plantar aponeurosis. The plantar aponeurosis, via dorsiflexion of the toes, contributed the most significant arch support in the sagittal plane with a 3.6 degrees increase between the first metatarsal and talus at 350 N and a 2.3 degrees increase at 700 N. The posterior tibialis tendon consistently provided arch support at plantar loads of 350 N and 700 N. The peroneus longus consistently abducted the forefoot in the transverse plane at 350-N and 700-N load levels. The study provides further insight into the dynamic supporting and deforming forces of the longitudinal arch.

The treatment of aneurysmal bone cyst.

Abstract: Forty-four patients with aneurysmal bone cysts were treated with curettage with or without bone grafting, and in 26 (59%) recurrence developed. Of 11 patients treated with radiation, in only 1 (9%) the disease was not controlled. In 1 patient, radiation-induced sarcoma developed. Since the introduction of cryosurgery 27 years ago, 51 patients have been treated with cryosurgery. The patients had an average age of 13 years (range, 2-32 years). Thirty-four primary aneurysmal bone cysts and 17 secondary aneurysmal bone cysts occurred in association with 7 giant-cell tumors, 5 chondroblastomas, 2 fibromyxomas, 2 nonossifying fibromas, and 1 unicameral bone cyst. The tumors were classified as inactive in 9 patients, active in 31, and aggressive in 11. Treatment consisted of local intralesional excision followed by application of liquid nitrogen. The defect was either allowed to heal spontaneously (n = 26) or was reconstructed using an intramedullary rod (n = 2), bone grafts (n = 5), fibular strut grafts (n = 14), or polymethylmethacrylate with Steinmann pins (n = 4). At median followup of 85 months (range, 24-311 months), the overall cure rate was 82%. This was increased to 96% after a second, or repeat, cryosurgery. The disease in all patients eventually was controlled by cryosurgery. The mean functional rating was 90% (range, 63%-100%). Intralesional excision with adjunctive cryosurgery is an effective method for the treatment of aneurysmal bone cyst.

Real-time calcium response of cultured bone cells to fluid flow.

Abstract: Using a parallel-plate flow chamber and fura-2 fluorescence microscopy, intracellular calcium was measured cell by cell in preconflu-ent primary culture rat calvarial bone cells to 18, 35, and 70 dynes/cm 2 of fluid-induced shear stress. A heterogeneous response with respect to peak amplitude and latency was observed for the culture, with an overriding dose-dependent relationship between the mean peak amplitude of response and shear-stress magnitude. A dose dependence was observed between the number of responsive cells (responding >50% over basal levels) and shear-stress magnitude. Not all cells could be restimulated by repeated exposure to flow. The observed cell response appears to be independent of whether cells are clustered together or isolated. Substratum stretch, hydrostatic pressure, and fluid shear stress have been shown in the literature to increase inositol phosphate (IP 3 ) in bone cells, with IP 3 causing the release of calcium from intracellular stores such as the endoplasmic reticulum. Therefore, a 6-fold inhibitory effect observed when calcium release from stores was blocked with 8-(n,N-diethylamino)octyl 1-3,4,5-atrimethoxybenzoate hydrochloride implicates an IP 3 biochemical pathway mediating the fluid flow response in bone cells.

Proximal third tibial shaft fractures. Should they be nailed

Abstract: Thirty-two extraarticular fractures of the proximal third of the tibia were treated with locked intramedullary nails. There were 10 closed and 22 open injuries. Treatment consisted of a reamed nail in each of the 5 closed fractures, and an unreamed nail in the remaining 27 fractures. Thirty of the 32 fractures eventually healed; however, 9 (28%) underwent exchange nailing and 4 (13%) required bone grafting. At final followup, 27 of 32 fractures (84%) had angulation of 5 degrees or greater in the frontal or sagittal plane. Nineteen of the 32 fractures (59%) had 1 cm or more of displacement at the fracture site. In 8 fractures (25%), there was loss of fixation, most commonly associated with placement of a single proximal locking screw. Fractures of the proximal third of the tibial shaft do not appear to respond as favorably to intramedullary nailing as do fractures in the distal 2/3 of the tibia. Valgus, apex anterior angulation, and residual displacement at the fracture site are common after nailing. Surgical errors of a medialized nail entry point and a posteriorly and laterally directed nail insertion angle contributed to malalignment. Based on their findings, the authors have limited the use of intramedullary nailing for proximal third tibial shaft fracture and consider alternate forms of fixation (plate or external fixation).

The nerve endings of the acetabular labrum.

Abstract: The nerve endings of the human acetabular labrum were investigated. Twenty-three acetabular labra were obtained from 24 fresh human cadavers, stained with Suzuki's silver impregnation and an immunohistochemical technique for neurogenic specific protein S-100, and examined by light and electron microscopy. Ramified free nerve endings were seen in all specimens by silver staining, and also were observed by the immunohistochemical technique for S-100 protein. Sensory nerve end organs, such as a Vater-Pacini corpuscle, Golgi-Mazzoni corpuscle, Ruffini corpuscle, and articular corpuscle (Krause corpuscle), were observed by silver staining. Collagen fibers were scattered sparsely in the superficial layer of the labrum, and nerve endings were observed mostly in this region. Collagen fibers were sparse, and nerve endings also were observed in some regions among the collagen fiber bundles in the inner layer. Innervation of the acetabular labrum was confirmed in this study, suggesting that nerve endings in the labrum may be involved in nociceptive and proprioceptive mechanisms.

The resistant frozen shoulder. Manipulation versus arthroscopic release.

Abstract: Frozen shoulder is often a self-limited disease, but approximately 10% of patients have long-term problems. Arthroscopy was done in 40 patients with persistent pain, stiffness, and functional loss for at least 1 year without improvement despite conventional treatment. In the first 20 patients, manipulation was done with an arthroscopy before and afterward ; in the second 20 patients, the contracted structures were divided through arthroscopy. This was a prospective cohort study ; 2 patients were not available for followup. The arthroscopic division procedure was done in 4 sequential steps : (1) resection of the inflammatory synovium in the interval area between the subscapularis and supraspinatus ; (2) progressive division of the anterior superior glenohumeral ligament and anterior capsule ; (3) division of the subscapularis tendon but not muscle ; and (4) division of the inferior capsule. The results were assessed independently on the basis of pain, stiffness, and function. The followup varied from 2 to 5 years after intervention. Patients treated with arthroscopy and manipulation did as well as the patients treated with arthroscopic division for restoration of range of movement. However, the patients in the arthroscopic division group had significantly better pain relief and restoration of function. Fifteen of 20 patients treated with arthroscopic division had an excellent result compared with 7 of 18 patients treated with arthroscopy and manipulation. Patients with diabetes did worse initially, but the outcome was similar to patients without diabetes. Patients with diabetes in particular may benefit from early intervention.

Local and distant products from modularity.

Abstract: In this study, the local and distant distribution of solid and soluble products of corrosion from the head and neck junction of modular femoral total hip prosthetic components were characterized. Particulate corrosion products from retrieved implants and surrounding tissues were analyzed. Serum transport and urinary excretion of metal was measured in correlation with the degree of corrosion at the head and neck junction. Particles of metal oxides, metal chlorides, and chromium phosphate corrosion products were identified on implants of 10 designs from 6 manufacturers. The most abundant solid corrosion product on the implant and within the periprosthetic tissues (size range, < 1-200 micrometers) was an amorphous chromium orthophosphate hydrate-rich material. Serum cobalt and urine chromium concentrations were elevated significantly in patients with implants that had moderate to severe corrosion in comparison with those with no to mild corrosion. Solid corrosion products from modular femoral stems may accelerate articular wear via a 3-body mechanism. Phagocytosable particles of these corrosion products may stimulate macrophage-mediated periprosthetic bone loss. Systemic dissemination of metallic corrosion products raises the issue of systemic toxicity; however, no overt evidence of metal toxicity was observed in this study.

Impact of gamma sterilization on clinical performance of polyethylene in the hip

Abstract: Despite studies to determine their causes, significant variations in polyethylene acetabular component wear rates, radial cracking of component rims, and occasional delamination cannot be explained. A subsurface white band frequently occurs in such damaged components. These damaged components often are gamma sterilized. To date, the origin of the band and its effect on polyethylene chemical and mechanical properties, and hence, clinical performance, have not been confirmed, and correlations between radiation sterilization and clinical wear have not been made. By developing techniques for polyethylene retrieval testing and rating, chemical analysis, and mechanical analysis, this research has determined that gamma sterilization in air alters the chemical and mechanical properties of polyethylene over time, resulting in high subsurface oxidation, reduced ductility, and reduced strength. Gamma sterilization-induced oxidation is found to be most severe in the subsurface region of components, and coincides with zones of significantly reduced strength and ductility. This chemical and mechanical property degradation is time dependent and is not typically visible until after 3 years' postirradiation. The presence of the subsurface white band significantly correlates with clinical cracking and delamination observed in retrieved components. Wear of the retrieved components often is observed to have progressed into this heavily oxidized, weakened, and embrittled zone. A method for accelerated aging shows that irradiating in air causes oxidation damage in polyethylene components that is not seen with other sterilization methods. Modifications of gamma sterilization techniques to minimize this damage are discussed.

Repair of complete acromioclavicular separations using the acromioclavicular-hook plate.

Abstract: Complete Tossy III acromioclavicular separations in 21 male patients (according to the Rockwood classification: 7 Type III and 14 Type V lesions) with a mean age of 31 years were treated by surgical repair with the acromicroclavicular-hook plate within a period of 6 years. The population consisted o

Injectable bone marrow preparations to stimulate osteogenic repair.

Abstract: The great versatility of bone marrow transplants based on stem cell activity has been demonstrated successfully for a variety of previously untreatable hemopoietic conditions. Autologous bone marrow delivered by percutaneous injection or by direct transplant as a composite graft also has proven effective for osteogenic stimulation in a series of 100 skeletal healing problems, including delayed unions and nonunions of fractures, arthrodeses, and bone defects. The efficiency of marrow to form bone can be increased by a number of methods, including differential centrifugation and composite grafts of marrow with demineralized bone matrix and other carriers or stimulatory factors.

Measurement of polyethylene wear in metal-backed acetabular cups. I. Three-dimensional technique.

Abstract: A new technique, the 3-dimensional technique, has been developed. Using a digitzer, points taken from anteroposterior and lateral radiographs are input into a personal computer. A 3-dimensional solid model of the prosthesis is created using custom software. Tilt and anteversion of the acetabular cup are measured, and the model is rotated to a standard frontal view, allowing measurement of femoral head displacement from the center of the acetabular cup. Comparing serial radiographs of the same patient gives the direction and distance of femoral head displacement over time, and this value is used to calculate the minimum volume of polyethylene debris generated. The 3-dimensional technique has been validated by construction of a precision acrylic phantom, and milling of a metal-backed acetabular cup to simulate polyethylene wear. Three-dimensional measurement of femoral head displacement using this technique has an accuracy of ±0.15 mm, and volume calculations are within 8% of the true amount of polyethylene removed from the cup. The 3-dimensional technique gives previously unavailable information, and can be used for clinical evaluation of polyethylene wear and evaluation of new prosthetic designs and bearing surfaces.

Titanium as the material of choice for cementless femoral components in total hip arthroplasty.

Abstract: Modern total hip arthroplasty has been performed using femoral stems manufactured from stainless steel, cobalt-chrome molybdenum alloy (CoCrMb), titanium aluminum vanadium alloy (TiAlV), and, on a limited basis, low-elastic modulus composites. Today, only CoCrMb and TiAlV are used in significant numbers. There is ample theoretical, experimental, and clinical evidence to support Ti-AlV as the material of choice for cementless femoral stems, based on superior mechanical compatibility and biocompatibility. The primary advantage of TiAlV over CoCrMb is a lower modulus of elasticity. This results in decreased stress shielding and subsequent favorable femoral remodeling. This effect is more significant with the smaller stem sizes used in primary surgery but persists even with larger stem sizes used in revision surgery. The second advantage of TiAlV is its biocompatibility. Titanium aluminum vanadium alloy is of relatively low toxicity in concentrations found clinically, and TiAlV is inert in the physiologic environment. With regard to fixation in cementless total hip arthroplasty, TiAlV has been shown to achieve excellent bone ingrowth into porous surfaces. In addition, there is evidence of superior bony ingrowth into TiAlV as compared with CoCrMb. Titanium aluminum vanadium alloy is presently the material of choice to be used in conjunction with hydroxyapatite coating. Prosthetic design, stem diameter, and porous-coating applications play significant roles in bony response regardless of metal composition.

Femoral revision hip arthroplasty with uncemented, porous-coated stems.

Abstract: One hundred seventy-five cementless femoral hip revision surgeries with extensively porous-coated stems and 161 concomitant acetabular revisions done from 1984 to 1991 were retrospectively reviewed. Average age at surgery was 62.4 years. Followup ranged from 2 to 10 years (average, 5 years). One hundred sixty-eight femoral components (96%) remain in place. Two unstable components, 1 stable fibrous component, and 1 bone ingrowth component were painful and required rerevision. Two femoral components were removed as part of resection arthroplasties for repetitive acetabular failure caused by pelvic dissociation. One component was removed for late hematogenous infection. Using the Engh radiographic criteria, femoral stems were judged to have achieved bony ingrowth in 82.8% (n = 174) of the cases. Bony ingrowth occurred more frequently when the canal was filled with the prosthesis and with lesser degrees of bone stock deficiency. Severe stress shielding occurred in 11 (7.6% ; n = 144) of the bone ingrown cases and correlated with preoperative osteoporosis and larger diameter prosthesis. Significant thigh pain was less common in the bone ingrown (4.2% ; n = 144) than in the stable fibrous group (18.5% ; n = 27). Significant thigh pain in bone ingrown stems was more likely to occur with osteoporotic and bone stock-deficient femurs. To date, significant wear and osteolysis have not been observed.

Reconstruction Using the Saddle Prosthesis Following Excision of Primary and Metastatic Periacetabular Tumors

Abstract: From 1988 to 1991, 17 patients with malignant periacetabular tumors underwent limb-sparing surgery and reconstruction using the saddle prosthesis. There were 8 patients with primary malignant lesions (Group 1), and 9 patients with metastatic or systemic tumor involving the periacetabular pelvis (Group 2). All resections included excision of the acetabulum. Patients ranged in age from 24 to 76 years (average, 59.8 years). Local control was achieved in all patients. Wide margins were obtained in all patients with primary pelvic tumors. Functional outcomes were rated as follows excellent (10), good (2), fair (1), and poor (4). Three patients, all of whom had pulmonary metastasis before surgery, died within 8 months of surgery. Of the remaining 14 patients, 5 patients died between 6 and 28 months after the index procedure. At the end of the followup period, 9 patients were still alive (6 in Group 1 and 3 in Group 2), with a followup period ranging from 15 to 62 months (average, 33.4 months). The overall results for surviving patients were 7 excellent and 2 good results, with no fair or poor results.

Stresses in polyethylene components of contemporary total knee replacements : Polyethylene wear

Abstract: Contemporary knee designs differ considerably in the conformity that exists between the articulating surfaces of the femoral and tihial components. The thickness of the polyethylene components also varies from design to design. Conformity and thickness affect the stresses associated with surface damage and the subsequent generation of harmful polyethylene debris. In this study, the stresses and strains caused by contact were calculated for 8 contemporary knee prostheses. Finite element analysis using large-strain theory was used to determine the stresses and strains for the minimum available polyethylene thickness and for the knee in flexion. The greatest differences among designs was for the von Mises strain, which reached its maximum beneath the surface. The differences in stresses were less notable because of the nonlinear matcrial behavior of the polyethylene. This study also confirmed the advantages of designs that have more conforming articulating surfaces and thicker polyethylene components.

The effect of aging on the shape of the proximal femur.

Abstract: The design of cementless femoral prostheses is based on the assumption that age and gender do not affect the shape of the proximal femur. To test this hypothesis, standard anteroposterior and lateral radiographs were prepared of 4 sets of 20 femora, obtained from young (range, 40-60 years) and elderly (range, 60-90 years) donors of both genders. The intracortical and extracortical borders of each femur were digitized electronically, and key parameters were measured to define the shape and dimensions of the medullary canal and the position of the femoral head. Systematic differences were observed between the size and shape of male and female femora. Extracortical dimensions were larger in the male femora by 14% to 19%, and endosteal dimensions by 11% to 24%. However, there were no significant differences between the canal shape of young male and young female femora in the coronal, sagittal, or transverse planes. The male femora displayed no significant differences in canal shape or endosteal width as a function of age. Profound differences were observed in the endosteal shape and diaphyseal dimensions of the young and old female femora. The older female femora had wider canals at the level of the isthmus, with a significant reduction in the canal flare index (the ratio between the canal width proximal to the lesser trochanter and at the isthmus). This study demonstrates that cementless femoral prostheses of 1 standard shape cannot provide a close fit to the endosteal contours of young and elderly women.

Exposure in difficult total knee arthroplasty using tibial tubercle osteotomy.

Abstract: Exposure with an extended tibial tubercle and tibial crest osteotomy was done for 136 total knee arthroplasties from 1986 to 1994: There were 26 primary arthroplasties, 76 revision, 10 repeated revision, 19 infected, and 5 repeated revision for infection. Adequate exposure was achieved and further release of the quadriceps mechanism was not necessary. Two or 3 wires were passed through the lateral edge of the tibial tubercle and through the medial tibial cortex to reattach the bone fragment and patellar tendon. Mean range of motion in these cases at 2 years after surgery was 93.7 degrees (range, 15 degrees-140 degrees). Two knees had extension lag, unchanged from their preoperative condition. Two tibial tubercles had partial proximal avulsion fracture, but did not separate widely. No evidence of non-union occurred in the simple cases or in the infected cases in which repeat elevation of the tibial tubercle flap and quadriceps mechanism was done. Three wires were removed because of pain. Two tibial fractures occurred in a single patient with diabetic Charcot arthropathy, and in 1 with manipulation after open adhesiolysis. Quadriceps function was not compromised in any case. Knees with Charcot arthropathy may need prolonged protection from weightbearing. Special caution should be exercised when manipulation is done to improve knee flexibility.