Learning curve for active robotic total knee arthroplasty

PURPOSE

Total Knee Arthroplasty (TKA) procedures incorporate technology in an attempt to improve outcomes. The Active Robot (ARo) performs a TKA with automated resections of the tibia and femur in efforts to optimize bone cuts. Evaluating the Learning Curve (LC) is essential with a novel tool. The purpose of this study was to assess the associated LC of ARo for TKA.

METHODS

A multi-center prospective FDA cohort study was conducted from 2017 to 2018 including 115 patients that underwent ARo. Surgical time of the ARo was defined as Operative time (OT), segmented as surgeon-dependent time (patient preparation and registration) and surgeon-independent time (autonomous bone resection by the ARo). An average LC for all surgeons was computed. Complication rates and patient-reported outcome (PRO) scores were recorded and examined to evaluate for any LC trends in these patient related factors.

RESULTS

The OT for the cases 10-12 were significantly quicker than the OT time of cases 1-3 (p < 0.028), at 36.5 ± 7.4 down from 49.1 ± 17 min. CUSUM and confidence interval analysis of the surgeon-dependent time showed different LCs for each surgeon, ranging from 12 to 19 cases. There was no difference in device related complications or PRO scores over the study timeframe.

CONCLUSION

Active Robotic total knee arthroplasty is associated with a short learning curve of 10-20 cases. The learning curve was associated with the surgical time dedicated to the robotic specific portion of the case. There was no learning curve-associated device-related complications, three-dimensional component position, or patient-reported outcome scores.

LEVEL OF EVIDENCE

Level II.

Active robotic technologies for total knee arthroplasty

INTRODUCTION

When active robotic technologies for Total Knee Arthroplasty (TKA) were introduced over 20 years ago, broad usage of robotic technology was not felt to be needed as early data suggested no clear improvement in clinical outcomes compared to conventional techniques of implantation. Only recently has there been renewed enthusiasm for use of robotic technologies for implantation.

MATERIALS AND METHODS

Active robotic technology specifically refers to the use of a robot for planning and executing the surgical procedure-with surgeon guidance and control. The physical work of bone preparation is performed by a milling tool, following a cut path defined by a CT-based preoperative plan. This manuscript describes the IDE experience of the only active robotic system (ARoS) available in the US, which took place from February 2017 through December 2018.

RESULTS

115 patients were enrolled in an IDE study to evaluate the safety and efficacy of an ARoS for TKA. No previously described safety issues for TKA occurred. Three-dimensional accuracy of component placement used the preoperative CT plan compared to the 3-months postoperative CT scan to demonstrate accuracy of all autonomous resections to within 1.5 mm and/or 1.5 degrees. Surgical planning and execution to restore alignment along kinematic principles were used in 40 procedures and to achieve mechanical alignment in 75 procedures.

CONCLUSIONS

This FDA study of an active robotic approach for TKA represented the first multicenter trial and first US experience with this technology. Results demonstrated an excellent safety profile and high degree of accuracy. Advantages of this approach relate to standardization of the technique, multiple device options in the implant library, an excellent safety and accuracy profile, and consistency of results. Active robotics for TKA represents a viable and safe technique for primary TKA.

Accuracy and precision in resection alignment: Insights from 10,144 clinical cases using a contemporary computer-assisted total knee arthroplasty system

BACKGROUND

Studies on total knee arthroplasty (TKA) with computer-assisted orthopedic surgery (CAOS) are limited by sample size or overlooked longitudinal performance of the system. This study aimed to assess resection accuracy across the entire TKA application history of a modern CAOS system considering multiple factors.

METHODS

A retrospective analysis was performed based on a database that archives technical logs of all TKAs performed using a CAOS system. Coronal resection errors and percentage of outliers (<2° alignment error) in the proximal tibia and distal femur were assessed. Multilevel modeling was used to understand whether and where the resection error variability was located in the grouping categories, which included geographic region, individual established surgeon, preoperative alignment, adoption phase (learning/proficient), and version of the CAOS software application.

RESULTS

A total of 10,144 cases were reviewed. The accuracy (mean) and precision (standard deviation) of the coronal alignment for both the tibia and femur were at the sub-degree level. High percentages of acceptable resections were observed across the pooled and each grouping category. The accountability for the amounts of total variability in tibial and femoral resection errors was negligible for all grouping categories, demonstrated by ICC values less than the common variations in observational studies.

CONCLUSIONS

The study applied advanced analyses to assess alignment outcome in TKA bony resection alignment across the history of a specific CAOS system. The results demonstrated high resection alignment accuracy insensitive to geographic region, CAOS software application, adoption phase, preoperative alignment, and inter-surgeon differences.

Techniques for periarticular infiltration with liposomal bupivacaine for the management of pain after hip and knee arthroplasty: a consensus recommendation

Periarticular infiltration analgesia when used as a component of multimodal analgesia regimen has been shown to provide excellent pain relief after major joint replacement surgery. Recently, a liposomal formulation of bupivacaine (Exparel) has been approved for administration into the surgical site to produce postsurgical analgesia. It is a sustained release preparation of bupivacaine that has been shown to provide pain relief for up to 72 hours with a single local administration. Because the success of infiltration technique depends on systematic, extensive, meticulous tissue injection before surgical wound closure, a group convened to address the best practice for periarticular injection techniques for hip and knee replacement surgery. This article provides recommendations for optimal solution for injection (i.e., drug combinations or ``cocktail'' and total volume) as well as detailed description (including illustrations) of the infiltration technique for primary, revision, and unicompartmental knee arthroplasty and primary and revision hip arthroplasty using various surgical approaches.

Improving patient outcomes through advanced pain management techniques in total hip and knee arthroplasty

Pain following orthopedic surgery is common and often suboptimally managed, with many patients reporting acute moderate to severe pain following surgery. Opioids are often used to manage this pain, yet this can result in significant side effects and complications, including constipation, nausea, vomiting, respiratory distress, and other central nervous system issues. Multimodal therapy that includes surgical site infiltration with extended release local anesthetic has been seen as a new way to minimize this pain for patients, which can result in improved quality of life and shorter length of hospital stay. This article examines the use of bupivacaine liposome injectable suspension (EXPAREL®; Pacira Pharmaceuticals, Inc., San Diego, California), a non-opioid product for pain management. Liposomal bupivacaine uses DepoFoam® technology that allows for the extended release of injected drugs. When used as the foundation of a multimodal regimen, it is effective in reducing postsurgical pain for up to 72 hours while reducing the need for opioids for pain relief.

Bilateral patellar component shear failure of highly cross-linked polyethylene components: report of a case and laboratory analysis of failure mechanisms

A case of bilateral patellar component failure due to fatigue fracture of the all-polyethylene fixation pegs in a highly cross-linked ultra-high-molecular-weight polyethylene design is presented. To recreate this failure mode, a novel test method was developed to investigate the effects of peg orientation and cement technique on patella fatigue strength under cyclic compression and shear loading. Patellar peg orientation had a minor effect on shear strength, whereas lack of cement in the backside patellar groove had a substantial effect. The shear fatigue strength exceeded in vivo force estimates when the patellar groove was fully cemented. The test results and retrieval analysis suggest that high activity level and inadequate cement fixation of the patellar component may contribute to all-polyethylene patellar component peg fractures.

Early return to function after hip resurfacing: is it better than contemporary total hip arthroplasty?

Our hypothesis was that return of function for young patients undergoing resurfacing total hip arthroplasty (THA) with metal-on-metal bearings or contemporary THA with ceramic bearings would be comparable. Results from 337 unilateral hip resurfacing patients were compared with results from 266 unilateral ceramic-on-ceramic THA patients. Early differences in Harris Hip Scores were observed, but all differences faded by 24 months. Hip resurfacing seems to be a viable alternative to THA for well-selected patients. However, the public perception of improved functional capabilities was not demonstrated in this patient population. Resurfacing patients may be more impaired (slightly higher pain scores/lower function scores) than their THA counterparts in the early postoperative period, but these differences disappear by 24 months when both groups report Harris Hip Scores in the excellent range.

Resurfacing arthroplasty for patients with osteonecrosis

The suitability of third-generation metal-on-metal hip resurfacing products for patients with a primary diagnosis of osteonecrosis has been debated. The preservation of femoral head bone stock for femoral prosthetic support is essential for the long-term stability of implants. A modern hip resurfacing system was implanted in 1148 hips as part of a United States multicenter investigational device exemption study. Of these, 116 hips had a preoperative diagnosis of osteonecrosis and were compared to 1023 hips with osteoarthritis. Survival rates were not significantly different (95.9% and 95.8% at 24 months for osteoarthritis and osteonecrosis respectively, p = 0.46). Resurfacing arthroplasty for patients with osteonecrosis appears to be a reasonable alternative, taking into consideration implant size, patient gender, and size of femoral deficiency. Further characterization is needed to identify those specific patients with osteonecrosis for whom resurfacing arthroplasty would be appropriate.

Results and lessons learned from a United States hip resurfacing investigational device exemption trial

BACKGROUND

Improvements in metal-on-metal bearings have made hybrid hip surface replacement a potential alternative for the young active patient with end-stage hip disease. Possible advantages include greater hip joint stability, bone preservation, and decreased osteolysis. In this study, we compared the clinical and radiographic results of a new resurfacing device with those in a historical group of standard total hip arthroplasties.

METHODS

In 2001, the Cormet 2000 Hip Resurfacing Investigational Device Exemption study was initiated at twelve centers. A total of 337 patients treated with unilateral hip surface replacement with the Cormet device were enrolled in that study. These patients were compared with 266 patients in a previous study who had undergone unilateral total hip arthroplasty with ceramic bearing surfaces. Clinical and radiographic results were compared at similar time intervals. A newly recommended performance standard, the composite clinical success score, was used to assess non-inferiority of the hip resurfacing compared with the total hip arthroplasty used in the historical comparison population.

RESULTS

At the time of follow-up, at a minimum of two years, the Harris hip scores were comparable between the resurfacing and total hip arthroplasty groups. Statistical evaluation of the composite clinical success scores confirmed the non-inferiority hypothesis. Revision was required in twenty-four patients in the resurfacing group and five patients in the total hip arthroplasty group. The most common cause of revision following resurfacing was failure of the femoral component (fracture of the femoral neck or loosening of the femoral component).

CONCLUSIONS

Careful review of this study population revealed several important criteria for successful introduction of this resurfacing device into the United States. These include careful patient selection based on clinical and radiographic parameters and attention to various surgical details of implantation. These findings can be used to focus the training process for surgeons who wish to add implantation of this device to their surgical armamentarium. Such efforts should help to ensure safe and effective introduction of this new technology.

Blood management issues using blood management strategies

Blood management strategies is a term used to address a coordinated approach to the management of blood loss in the perioperative period for total joint arthroplasty. The premise of any blood management strategy is that each patient, surgeon, and operative intervention experiences different risks of requiring transfusion, that those risks can be identified, and that a plan can be implemented to address them. A surgeon's decision to transfuse should be based on physiologic assessment of the patient's response to anemia and not on an arbitrary number ("transfusion trigger"). Intervention strategies can be applied preoperatively, intraoperatively, and postoperatively. Patient-specific planning allows for the appropriate use of patient, hospital, and system resources, ensuring that the consequences of anemia are minimized and that the patient's recovery process is optimized.

Physical therapy alone compared with core decompression and physical therapy for femoral head osteonecrosis in sickle cell disease. Results of a multicenter study at a mean of three years after treatment

BACKGROUND

Osteonecrosis of the femoral head is a common complication in patients with sickle cell disease, and collapse of the femoral head occurs in 90% of patients within five years after the diagnosis of the osteonecrosis. However, the efficacy of hip core decompression to prevent the progression of osteonecrosis in these patients is still controversial.

METHODS

In a prospective multicenter study, we evaluated the safety of hip core decompression and compared the results of decompression and physical therapy with those of physical therapy alone for the treatment of osteonecrosis of the femoral head in patients with sickle cell disease. Forty-six patients (forty-six hips) with sickle cell disease and Steinberg Stage-I, II, or III osteonecrosis of the femoral head were randomized to one of two treatment arms: (1) hip core decompression followed by a physical therapy program or (2) a physical therapy program alone. Eight patients withdrew from the study, leaving thirty-eight who participated.

RESULTS

Seventeen patients (seventeen hips) underwent decompression combined with physical therapy, and no intraoperative or immediate postoperative complications occurred. Twenty-one patients (twenty-one hips) were treated with physical therapy alone. After a mean of three years, the hip survival rate was 82% in the group treated with decompression and physical therapy and 86% in the group treated with physical therapy alone. According to a modification of the Harris hip score, the mean clinical improvement was 18.1 points for the patients treated with hip core decompression and physical therapy compared with 15.7 points for those treated with physical therapy alone. With the numbers studied, the differences were not significant.

CONCLUSIONS

In this randomized prospective study, physical therapy alone appeared to be as effective as hip core decompression followed by physical therapy in improving hip function and postponing the need for additional surgical intervention at a mean of three years after treatment.

What would you do? Challenges in hip surgery

The panel reviewed cases involving both revision and primary total hip arthroplasties. The panelists are Hugh Cameron and Allan Gross from Toronto, Charles Engh from Arlington, Aaron Rosenberg from Chicago, and Bernard Stulberg from Cleveland. The cases discussed brought up some controversial issues.

Computer-assisted surgery: a wine before its time: in opposition

Total knee arthroplasty (TKA) surgery has achieved a high degree of success since the introduction of concepts of alignment and ligament balance in the early 1970s. Continuing pressure to improve function and longevity from the operative intervention has led to the design of increasingly sophisticated devices placed with the use of mechanical jigs. Although significant improvement has been made, errors of alignment and stability remain. Methods to diminish the margin of error have not been substantially improved with mechanical jigs, suggesting that intraoperative feedback is difficult to teach and learn, and resulting decision making is not as predictable as one would hope. This discussion will suggest why computer-assisted TKA may be the right answer to improving the predictability of TKA.

Clinical Evaluation of Avascular Necrosis in Patients With Sickle Cell Disease: Children’s Hospital Oakland Hip Evaluation Scale—A Modification of the Harris Hip Score

OBJECTIVE

To establish the validity and reliability of the Children's Hospital Oakland Hip Evaluation Scale (CHOHES), a modification of the Harris Hip Score, for the evaluation of avascular necrosis (AVN) in sickle cell disease (SCD).

DESIGN

Nonrandomized test-retest.

SETTING

Outpatient clinic.

PARTICIPANTS

Forty patients with SCD and 3 healthy controls participated. Twenty-six SCD patients (15 males, 11 females; mean age, 25 y) had been diagnosed with AVN. This group was compared with 14 SCD patients without AVN and 3 healthy controls (8 males, 9 females; mean age, 16 y).

INTERVENTION

On average, subjects were assessed by 2 physical therapists by using the CHOHES on 3 separate outpatient visits within a 2-week period.

MAIN OUTCOME MEASURES

A mixed model with random effects was constructed to compare patient scores on the CHOHES with disease severity as estimated by Ficat staging on plain radiographs. Correlations between and within physical therapists using the CHOHES were calculated to assess intra- and interrater reliability.

RESULTS

From the random effects model, the CHOHES mean score was 88 for Ficat stage 0, 75 for Ficat stage I or II, and 61 for Ficat stages III or IV (P < .05). Intrarater reliability estimates for the total CHOHES score were very good (r > or = .87) as were interrater reliability estimates (r > or = .90) between therapists who measured hips with a wide range of CHOHES scores.

CONCLUSIONS

The CHOHES appears to be an easy-to-use, valid, and reliable assessment tool and should be considered for use in the routine clinical evaluation of SCD patients with AVN.

Osteonecrosis: what to do, what to do!

Despite extensive literature on the subject, the treatment approaches for osteonecrosis of the femoral head (ONFH) remain controversial. The literature presently available to the orthopaedist suggests that i) ONFH can be identified early; ii) there are reasonable treatments for early stages of ONFH; iii) no single treatment is sufficient for all hips; and iv) there is as yet no predictable permanent treatment for early ONFH. The author's recommended approach for the practicing orthopaedist includes the following: i) develop a high degree of clinical suspicion that the disease is present and understand the role of magnetic resonance imaging in making an accurate diagnosis; ii) understand and use an appropriate staging system for each hip diagnosed; iii) be comfortable with several treatment options for early ONFH or choose to refer to appropriate centers; and iv) become comfortable with the use of uncemented THA for end-stage ONFH. The field continues to need and should support better treatment studies, including randomized clinical trials.

Histologic evaluation of posterior cruciate ligaments from osteoarthritic knees

It is controversial whether posterior cruciate ligament-retaining or posterior cruciate ligament-sacrificing (-substituting) implants should be used in total knee arthroplasty. The use of posterior cruciate ligament-retaining implants implies that the residual ligament is functional, and presumably normal, but few studies have been conducted to elucidate the histologic appearance of the posterior cruciate ligament taken from osteoarthritic knees. The purposes of the current study were (1) to evaluate the histologic appearance of posterior cruciate ligaments excised from osteoarthritic knees during primary total knee arthroplasty and to compare their appearance with posterior cruciate ligaments from knees of cadavers that were not operated on; and (2) to determine whether a correlation exists between the histologic appearance of the posterior cruciate ligament and the clinical status of the patients studied. Twenty-six posterior cruciate ligament specimens from patients with osteoarthritis and four specimens from cadavers were evaluated with the use of light and electron microscopy. Posterior cruciate ligaments from osteoarthritic knees showed greater degeneration than those from cadavers by light microscopy. Age greater than 60 years was associated with decreased collagen diameter in posterior cruciate ligaments from osteoarthritic knees as determined by electron microscopy. With the number of specimens available, the authors could not find a significant correlation between tibiofemoral alignment and mean collagen diameter or percentage of collagen occupancy. The extent of tissue degeneration of the posterior cruciate ligament could not be predicted by clinical findings. Additional studies identifying the mechanical competency of the posterior cruciate ligament in osteoarthritis would be valuable.

Multidirectional deformation in fully congruent acetabular components

Most clinical studies have used femoral head migration as an index of acetabular wear, but a previous study showed multiple wear vectors in 30% of retrieved acetabular components with noncongruent liners. The origin of multiple wear vectors is unclear, and it has been suggested that polyethylene creep in a noncongruent shell might influence deformation on the articular surface. We used shadowgraph and volumetric methods to evaluate the extent and direction of surface deformation of 37 retrieved polyethylene liners that were fully congruent to a single design of metal backing. The results show that multiple deformation vectors are relatively common in retrieved acetabular cups (27% in this study) and are independent of congruency between liner and metal backing, rim impingement, and backside creep. Polyethylene liners with multiple wear vectors were significantly thinner than those of cups with a single vector. The origin of multiple vectors is still unclear, but clinical and laboratory studies measuring linear wear alone without recognizing multiple vectors underestimate total in vivo volumetric wear.

Relationship between wear debris particles and polyethylene surface damage in primary total knee arthroplasty

To study relationships between design and wear, particles were isolated from tissues around 75 failed primary total knee prostheses, and particle size and concentration were compared with the extent and distribution of wear on superior and inferior polyethylene surfaces of the corresponding implants. Twenty-four heat-pressed, posterior cruciate ligament (PCL)-retaining (group I: PCA knee), 19 non-heat-pressed, PCL-retaining with relatively flat surfaces (group II: AMK, Kinematic, Microloc, Ortholoc), 14 non-heat-pressed, PCL-retaining with relatively congruent surfaces (group III: Townley Arizona), and 18 PCL-resected implants (group IV: Insall-Burstein, Total Condylar) were evaluated. Groups III and IV had fewer particles, smaller particles, and less surface damage than groups I and II. Implants with third-body wear had relatively small debris particles; those with thinner polyethylene had more severe surface delamination and more wear between liner and metal base. Groups I and II had more rotationally asymmetric wear patterns than groups III and IV. The size and concentration of debris particles might reflect, in part, different dominant wear mechanisms among implants of different designs.

Results of 2-stage reimplantation for infected total knee arthroplasty

Optimum treatment of the infected total knee arthroplasty has not been clearly established. To clarify the efficacy of two-stage reimplantation, experience with 66 infected total knee arthroplasties in 64 patients who had been treated with 2-stage reimplantation total knee arthroplasty between September 1980 and October 1993 was reviewed. Of these, 55 knees in 54 patients were available for follow-up examinations at an average of 61.9 months (range, 28-146 months). The initial diagnoses were rheumatoid arthritis (14 knees) and osteoarthritis (41 knees). Reimplantation was successful in 80.0% of knees with low-virulence organisms (coagulase-negative Staphylococcus, Streptococcus), 71.4% with polymicrobial organisms, and 66.7% with high-virulence organisms (methicillin-resistant Staphylococcus aureus). Reimplantation was successful in 82% of patients with osteoarthritis and in 54% of patients with rheumatoid arthritis (P = .024). The success rate was 92% if infection occurred after primary arthroplasty but only 41% if after multiple previous knee operations (arthroscopy, osteotomy, or revision total knee arthroplasty) (P < .001).

Effect of femoral head diameter on tissue concentration of wear debris

Although several studies have reported the physical properties of debris particles in tissues adjacent to failed total joint implants, few have correlated the results of particle analysis with other clinical and implant variables believed to influence implant wear. We retrospectively analyzed 41 fibrous membranes (from 35 patients) adjacent to failed acetabular cups from a single manufacturer and studied the relationship between three different femoral head sizes (26, 28, and 32 mm) and the characteristics of wear debris in the adjacent tissues. All total hip prostheses consisted of modular cobalt-chromium alloy femoral heads articulating with titanium-alloy-backed ultrahigh molecular weight polyethylene (UHMWPE) acetabular components from a single manufacturer. Large femoral head diameter (32 mm) was found to correlate significantly with large particle size (diameter and surface area, p < 0.05), high tissue concentration of particles (particle volume/gram of tissue, p < 0.01), and high rate of particle production (particles volume/month, p < 0.05). The results of these quantitative assays support the findings of radiographically based clinical studies that show higher volumetric wear associated with 32 mm femoral head components.

Prevention of deep-vein thrombosis after total hip arthroplasty. Comparison of warfarin and dalteparin

The effectiveness and safety of warfarin were compared with those of a low-molecular-weight heparin (dalteparin) for the prevention of deep-vein thrombosis after total hip arthroplasty in a prospective, randomized, multi-institutional trial. Patients who were older than eighteen years of age and were scheduled to have an elective primary or revision total hip arthroplasty were eligible; 580 patients were randomized, 550 had the operation and received prophylaxis, and 382 had evaluable venograms. Prophylaxis was provided either with warfarin beginning the night before the operation or with dalteparin beginning two hours before the operation and was continued until venography was performed. Bleeding was assessed on the basis of intraoperative blood loss, transfusion requirements, a decrease in hematocrit, and clinically identified bleeding complications. The prevalence of deep-vein thrombosis was found to be significantly lower in the patients who had received dalteparin than in those who had received warfarin (twenty-eight [15 per cent] of 192 patients compared with forty-nine [26 per cent] of 190 patients; p = 0.006). Deep-vein thrombosis occurred in the calf veins of twenty-one patients (11 per cent) who had received dalteparin and of forty-three patients (23 per cent) who had received warfarin; this difference was significant (p = 0.003). Proximal deep-vein thrombosis occurred in ten patients (5 per cent) who had received dalteparin and in sixteen patients (8 per cent) who had received warfarin; however, with the numbers available, no significant difference could be detected (p = 0.185). We also could not detect a significant difference with regard to the intraoperative and postoperative blood loss, the decrease in hematocrit, and the prevalence of major bleeding complications between the two groups; however, the patients who had received dalteparin had a significantly higher prevalence of bleeding complications involving the operative site (p = 0.03), and a significantly greater percentage required postoperative transfusions (p = 0.001). We concluded that preoperative prophylaxis with dalteparin is significantly more effective than that with warfarin in preventing deep-vein thrombosis after total hip arthroplasty. The greater effectiveness of dalteparin must be considered, however, in light of an increased need for postoperative transfusions and an increase in the prevalence of wound-related bleeding complications.

Uncemented total hip arthroplasty in osteonecrosis: a 2- to 10-year evaluation

All patients undergoing uncemented total hip arthroplasty for end stage hip disease related to osteonecrosis of the femoral head were assessed prospectively between November 1983 and October 1992. The results of clinical evaluation using the Harris Hip score and radiographic assessment of fixation were analyzed to identify features of success or failure that may be unique to this population. Four different stem types and 4 different acetabular components were used. Sixty-four patients had 98 hips implanted during the time of the study. The 42 male and 22 female patients averaged 41 years of age (range, 21-69 years). Average followup was 87.3 months (7.3 years; range, 31-134 months). The cause of osteonecrosis was corticosteroids (42 hips), alcohol (27 hips), trauma (5 hips), and other (24 hips). Three patients (5 hips) have died and 4 patients (6 hips) are lost to followup. At last followup 65 of 87 hips (75%) remained radiographically stable and clinically functional, 18 of 87 (21%) have been revised, and 4 were failing (osteolysis). Of the 22 hips with revision or impending failure, 4 were for technical reasons on the femoral side and 18 were for acetabular wear. Patient factors such as weight or underlying disease state did not seem to influence the ability to achieve stable fixation or contribute to accelerated failure. Failures related primarily to problems of first generation devices including accelerated wear of acetabular components, technical issues of femoral component placement (undersizing of components or femoral fracture), and the use of noncircumferentially coated femoral components. Age may be a factor in early failure. This 10-year experience with total hip arthroplasty for the patient with end stage hip disease due to osteonecrosis suggests that uncemented total hip arthroplasty can be applied predictably to this younger, potentially more active patient population.

Characterization of debris adjacent to failed knee implants of 3 different designs

Wear debris particles have been associated with bone resorption and loosening of total joint implants. To characterize the wear particles around failed knee prostheses, tissues adjacent to 47 implants of 3 different designs were evaluated: 29 were posterior cruciate ligament retention type (Group I), 12 were posterior cruciate ligament sacrificing or substituting (Total Condylar, Insall-Burstein), (Group II), and 6 were mobile bearing (posterior cruciate ligament retaining LCS), (Group III). Wear particles were isolated and evaluated using electronic particle quantitation and scanning electron microscopy. The corresponding implants were also evaluated, and the surface damage quantified. The number of particles smaller than 10 microm ranged from 8.9 to 45.8 x 10(9) per gram of tissue (dry weight). Particle number directly correlated with duration of implantation. Group I implants had larger particles, and showed greater surface damage than the other 2 designs. Polyethylene surface damage significantly correlated with particle size more than 10 microm in length. Particle number showed a significant inverse correlation with the thickness of the polyethylene. These results support previous mechanical and retrieval studies suggesting that increased wear may be associated with thinner polyethylene, and there are differing degrees and patterns of wear based on implant design.

Characterization and comparison of wear debris from failed total hip implants of different types

Particles of wear debris have been associated with loosening of implants and with osteolysis, but few studies have examined the relationship between characteristics of the implant and clinical variables and the concentration of particles isolated from periarticular tissues. We isolated and quantified particles of wear debris from orthopaedic implants in 123 tissue samples that had been obtained adjacent to a failed total hip prosthesis from eighty-eight patients. The concentration of these particles in the tissue and the size of the particles were then analyzed in relation to patient and implant-related variables. The number of particles ranged from 8.5 x 10(2) to 5.7 x 10(11) per gram of tissue (dry weight). More particles were found adjacent to failed titanium-alloy stems that had a cobalt-chromium-alloy modular head and failed titanium-alloy-backed cups than were found adjacent to all-cobalt-chromium-alloy prostheses. In addition, fewer particles were found adjacent to implants with a twenty-eight-millimeter femoral head than were found adjacent to implants with other femoral head sizes. Univariate analysis also showed correlations between a high concentration of particles and fixation without cement, an implant that had been in situ for a long duration, a young patient age, and an initial clinical diagnosis of avascular necrosis. Biopsy specimens from the proximal femoral membranes had higher concentrations than those from the joint capsules or the acetabular membranes. Although only five specimens were obtained directly from osteolytic lesions, the concentration of particles in those specimens was higher than that in biopsy specimens from other sites. Although many univariate correlations were identified, stepwise correlation regression analysis showed that the composition of the implant and the size of the modular femoral head were most strongly related to the concentration of debris in tissue.

Comparison and quantitation of wear debris of failed total hip and total knee arthroplasty

To compare the physical properties of debris particles associated with failed total hip and total knee arthroplasty, we applied a recently developed assay to electronically characterize the size, number, and composition of debris particles isolated from tissues adjacent to failed implants. We identified 21 samples (from 20 patients) of hip synovia and 35 samples (from 32 patients) of knee tissues that had been obtained at the time of revision arthroplasty. There were 12 females and 9 males in the hip group, and 16 females and 19 males in the knee group. Primary arthroplasty was performed for osteoarthritis (OA, 15 cases) or rheumatoid arthritis (RA, 6 cases) in the hip, and for OA (23) or RA (12) in the knee. Patients ranged in age from 23 to 85 (mean 59 years) for total hip, and from 27 to 84 (mean 61 years) for total knee arthroplasty. Implantation duration was from 5 to 123 months (mean 37.8) for total hip, and from 11 to 123 months (mean 63.1) for total knee arthroplasty. All of the implants were composed of cobalt-chromium alloy articulating with ultrahigh-molecular-weight polyethylene. The number of particles smaller than 10 microns ranged from 1.04 x 10(8)/g to 1.91 x 10(10)/g in the hip, and from 6.69 x 10(8)/g to 2.13 x 10(10)/g in the knee. Energy-dispersive X-ray spectroscopy and polarized light analysis showed both polyethylene and metal particles in most cases. The mean diameter of particles smaller than 10 microns was 0.72 +/- 0.2 microns in the hip, and 0.74 +/- 0.1 microns in the knee. Evaluation of particles larger than 10 microns showed a larger range of particle size in knee tissues (maximum 6.1 mm, mean 283 microns), than in the hip tissues (maximum 826 microns, mean 81 microns) (p < 0.001). Very small particles are common in both groups, but it appears that a larger range of particle sizes is present adjacent to failed knee than to failed hip prostheses. The higher frequency of large particles in failed knee prostheses probably reflects the perceived higher rate of delamination and fragmentation of tibial and patellar compared to that of acetabular polyethylene.

The porous-coated anatomic total hip prosthesis: failure of the metal-backed acetabular component

One hundred and ninety-nine total hip arthroplasties were performed, between 1983 and 1987, in 173 patients by three surgeons using the initial design of the porous-coated anatomic prosthesis. The acetabular component was a preassembled, metal-backed polyethylene device, with beads sintered to the metal backing to allow bone ingrowth and two pegs for initial fixation. Twenty-three acetabular components (12 percent) failed because of either migration or severe osteolysis. The radiographic appearance of osteolysis was positively associated with the duration that the implant had been in situ (p < 0.001). The prevalence of osteolysis was also significantly greater in acetabular components with an outer diameter of fifty-five millimeters or less (a polyethylene thickness of 8.5 millimeters or less) (p = 0.03). Thirteen hips were revised at a mean of 69.5 months (range, thirty-three to ninety-one months) after the index operation. Examination of the retrieved acetabular components revealed extensive polyethylene damage on the articular and back surfaces of the liners. Cracks in the polyethylene rim of the liner and deformation of the anti-rotation notch in the polyethylene rim were common findings. The density of the polyethylene was greater than expected, and more particles than anticipated had not fused with the surrounding polyethylene. The results of this study suggest that factors related to both the design and the material contributed to the failure of these porous-coated anatomic acetabular components.

Computed tomography analysis of proximal tibial coverage

Researchers of this study used computed tomographic studies of the proximal tibia for patients undergoing total knee arthroplasty to determine basic morphologic data of size, shape, and area of varying levels from the articular surface. Five off-the-shelf tibial component shapes (4 symmetric, 1 asymmetric) were templated to determine the fit of the components at the various resection levels. Seventy-two knees were assessed at 2-mm, 68 at 5-mm, 40 at 8-mm, and 17 at 11-mm resection levels. Significant differences in fit and percentage of total area of coverage were identified. Fit was significantly better for asymmetric as compared with the symmetric components (p = 0.001) at all levels of resection. Fit was significantly worse for each component as the resection depth increased. This information can serve as a bridge to clinical and laboratory data in identifying the importance of tibial component fit to the overall performance of a total knee arthroplasty design.

The use of muscle flaps for salvage of failed total knee arthroplasty

Deep infections occur in 1-5% of all patients undergoing total knee arthroplasty, and may result in failure of the prosthesis and subsequent arthrodesis. Two-stage reimplantation is often successful, but depends upon the presence of good soft tissue coverage. We have treated 9 patients in whom chronic infection developed which required removal of the prosthesis, debridement, and implantation of antibiotic impregnated spacers for control. These patients all had poor quality soft tissue cover precluding prosthesis reimplantation. The use of muscle flaps resulted in 7 of the 9 patients having successful reimplantation of a prosthesis and remaining free of infection in a follow-up ranging from 1-5 years.

Uncemented acetabular components. Histologic analysis of retrieved hydroxyapatite-coated and porous implants

Histologic sections of five hydroxyapatite-coated acetabular components retrieved at autopsy (2 dual geometry and 3 threaded cup designs) were analyzed, and the extent and pattern of bone apposition were compared with that of an uncoated, porous (beaded) dual geometry acetabular cup that had been removed for repeated dislocations. The results show hydroxyapatite and bone apposition most prominent in areas of likely load transmission, primarily around the peripheral rim of the dual-geometry cups and at the peaks of the threads of the screw cups. Hydroxyapatite and bone may have been removed by remodeling from the grooves between the threads. Although no significant wear debris was identified, the screw holes were incompletely covered by bone. The dual-geometry designs generally showed somewhat more bone apposition than the threaded cups, but all implants demonstrated less bone than might have been predicted from radiographs.

Preoperative nutritional status of total joint patients. Relationship to postoperative wound complications

The records of 217 consecutive patients who underwent a primary total hip or total knee arthroplasty were reviewed for preoperative and postoperative nutritional status. Fifty-seven patients had a lymphocyte count of less than 1,500 cells/mm3, four patients had an albumin level of less than 3.5 g/dL, and two patients had both, giving a 27% incidence of indices indicative of preoperative nutritional depletion. Patients without wound complications had an average preoperative lymphocyte count of 1,995 (+/- 631), compared to 1,638 (+/- 491) for those with persistent serous drainage from their wounds, and 1,553 (+/- 419) for those patients with a major wound complication (P = .002). The average albumin levels were 4.30 (+/- 0.33), 4.22 (+/- 0.31), and 4.13 (+/- 0.54), respectively. Patients with rheumatoid arthritis were compared to those with osteoarthritis and were found to have significantly lower preoperative albumin levels. They were three times as likely to develop a major wound complication. Patients on immunosuppressive medications had significantly lower preoperative lymphocyte counts, lower albumin levels, and higher complication rates (P = .04). After operation, lymphocyte counts of all patients dropped to an average of 57% of their preoperative values, and albumin levels dropped to 72% of their preoperative values. No nutritional parameters had returned to their preoperative levels by 10 postoperative days. For all patients, a preoperative lymphocyte count of less than 1,500 cells/mm was associated with a five times greater frequency of developing a major wound complication, and an albumin level of less than 3.5 g/dL had a seven times greater frequency.(ABSTRACT TRUNCATED AT 250 WORDS)

Osteonecrosis of the femoral head. A prospective randomized treatment protocol

Conservative treatment versus core decompression for cases of osteonecrosis (ON) of the femoral head was prospectively reviewed in 36 patients. A preoperative evaluation of the patients' history, physical examination, Harris Hip Score, roentgenograms, computed tomography, bone scan, magnetic resonance imaging, and measurement of the intraosseous pressure was used to grade the level of ON according to a rating system developed by Ficat. Hips were randomized to core decompression or conservative treatment groups. Fifty-five hips in 36 patients were randomized (29 surgical and 26 conservative). When success was gauged by Harris Hip Scores for Stage I hips, treatment was successful for seven of ten (70%) operatively treated hips and one of five (20%) non-operatively treated hips. Among Stage II hips, treatment was successful for five of seven (71%) decompressed hips and none of seven conservatively treated hips. Successful treatment was accomplished in eight of 11 hips (73%) and one of ten hips (10%) in decompression and conservative groups, respectively, for Stage III hips. Stages 0 and IV had groups too small for comparison. Less successful results were seen if roentgenographic criteria of success were used. Survival analysis showed more favorable results with surgical treatment. Core decompression produced better results than conservative treatment in the early stages of ON.

A new model to assess tibial fixation in knee arthroplasty. I. Histologic and roentgenographic results

A model to assess tibial fixation in knee arthroplasty is described. Eighteen mongrel dogs were implanted with a right tibial hemiarthroplasty. Implantation was of a press-fit, smooth implant (eight dogs) or a titanium alloy beaded device (ten dogs). Animals were studied at six, 12, 18, and 24 weeks. Roentgenographic and histologic analysis was performed for all implants. All animals were ambulatory. Roentgenographically, smooth implants showed progressive radiolucencies with increasing trabecular sclerosis under the implants. These changes were less prominent under the porous implants. Histologically, fibrous interfaces were identified focally under all implants but were thicker under smooth devices. Eighteen- and 24-week specimens showed substantial ingrowth into the porous pegs but minimal ingrowth into the porous plateau. Concurrent histologic and biochemical evaluation in dogs demonstrates the possible fate of implants in knee arthroplasty in human beings. As has been observed, histologic analyses suggest that clinically satisfactory results do not constitute evidence of stabilization by bone ingrowth.

A new model to assess tibial fixation. II. Concurrent histologic and biomechanical observations

A tibial hemiarthroplasty model was designed to allow concurrent histologic and biomechanical analysis of the tibial implant-bone interface. In this study, micromotion was visually observed at the implant-bone interface of cemented and uncemented implants. Six dogs had staged bilateral implantation. Biomechanical analysis of three- and 12-month specimens was correlated with histologic analysis of the same specimen. Load transmission involved compression of trabecular bone and fibrous tissue at the interface. Failure of the interface occurred through cyclic fatigue and microfracture of trabeculae. Micromotion was seen at all interfaces, porous or smooth, cemented or uncemented. Displacement was greatest under an eccentrically loaded plateau. Micromotion at ingrown and cemented interfaces was because of trabecular compression. Uncemented smooth devices and uncemented porous devices with fibrous fixation of the plateau appeared unstable. The cemented implants and a single uncemented implant studied at 12 months showed no interface micromovement. The absence of micromovement in the uncemented implant was associated with subsidence and with ingrowth of 30% into the porous peg and porous plateau.

Making core decompression work

Meaningful assessment of a treatment modality for osteonecrosis (ON) must take into account a number of factors: (1) an accurate diagnosis, (2) consistent staging of the disease process, (3) understanding of the variability of the disease, (4) consistent application of the treatment modality (or the surgical technique), and (5) a clear understanding of the goal of the treatment used. This article reviews the important steps of a diagnostic algorithm that has been used to accurately diagnose and stage the disease process of ON. A consistent surgical technique with clearly defined goals is also outlined. The results of two clinical studies that were based on these diagnostic and therapeutic philosophies and that assess the role of core decompression in the treatment of ON are reviewed. The first study compared core decompression to conservative management in a prospective randomized study of 55 hips. Decompression provided more predictable pain relief and changed the indications for further surgical intervention more consistently than did conservative management. The second study represents a preliminary review of a ten-year study of the decompression procedure; it showed that core decompression was particularly useful in Stage I and Stage II ON. Roentgenographic stabilization was most predictable for Stage I hips. Core decompression can be a safe, effective, and predictable procedure in the treatment of Stage I and Stage II ON.

Prevention of venous thrombosis after total knee arthroplasty. Comparison of antithrombin III and low-dose heparin with dextran

In a prospective, randomized trial, we compared the efficacy of a combination of antithrombin III and heparin with that of dextran 40 as prophylaxis against venous thrombosis after total knee arthroplasty. Ascending venography identified thrombosis in about one-third of the patients who received the combination of antithrombin III and heparin, compared with about four-fifths of those who received dextran (p less than 0.001). In both groups, the patients who had venous thrombosis had a significantly lower concentration of antithrombin III postoperatively than those who did not have thrombosis. Venous thrombosis occurred in all patients in whom the concentration of antithrombin III was less than 65 per cent postoperatively. These findings demonstrated that, after total knee replacement, the combination of antithrombin III and heparin effectively reduces the incidence of postoperative venous thrombosis and is significantly better than dextran. Furthermore, the findings suggested a relationship between postoperative deficiency of antithrombin III and the occurrence of thrombotic complications.

The incorporation of tibial allografts in total knee arthroplasty

Twelve knees in ten patients had revision total knee replacement with insertion of an allograft for a large tibial defect. The knees were retrospectively evaluated at an average of thirty-two months (range, twenty-five to fifty-one months) by clinical examination, radiography, planar bone scintigraphy, and single-photon-emission computed tomography. The average age of the patients was sixty-two years (range, fifty-four to seventy-nine years). A constrained total-condylar prosthesis was used for all revisions. A contained tibial defect was present in five knees, and seven knees had an uncontained defect that was treated with a massive composite structural allograft, five of which were secured with internal fixation. The knee scores improved from an average of 51 points before operation to an average of 87 points post-operatively. Seven knees had a score of 85 points or more and were considered to have an excellent clinical result. Two knees had a good result, with scores of 77 and 72 points. One knee had another revision because of painful non-union of a medial structural graft, and the result in that knee was considered a failure. The average range of motion improved from 84 degrees to 105 degrees. There were no deep infections, and no graft showed evidence of fracture or collapse. Radiographs demonstrated complete incorporation of the graft in eleven of the twelve knees at an average of twenty-three months after operation. Single-photon-emission computed-tomography scans showed uniform activity in the area of the graft in four of the five knees that were studied.

Expandable breast implant reconstruction of Tikhoff-Linberg shoulder deformity

Expanding breast implants were used in two patients to reconstruct shoulder contour following a Tikhoff-Linberg resection for cancer. In the first patient, one implant alone was used, and in the second patient, two implants in separate but adjacent pockets. The resulting double contour is more pleasing than that after a single implant, and there also appears to be more flexibility with shoulder motion. This method is suggested as an excellent means of reconstructing the contour of the shoulder area following resection for cancer.

The rationale, design characteristics, and preliminary results of a primary custom total hip prosthesis

Seventy-three primary custom-made uncemented hip implants have been inserted since July 1987. The initial clinical results are equivalent to those of conventionally made components, but there has been less residual and recurrent thigh pain with the custom devices. The custom implants have achieved 20% greater canal fill with much less variation than conventionally made devices. Custom components have been particularly useful in patients with significant anatomic deformity and associated arthritis.

A diagnostic algorithm for osteonecrosis of the femoral head

For patients considered at risk for osteonecrosis (ON) of the femoral head, an algorithm for the efficient and appropriate use of diagnostic tests can be developed. Such an algorithm requires a clear idea of the evolution of the disease process and an understanding of the limitations of each of the modalities by which the disease process can be identified. The role of each of the diagnostic tests available for the diagnosis of ON and the results of prospective evaluations to assess their sensitivity, specificity, and predictive values are reviewed. No single diagnostic test is 100% accurate in the diagnosis of the disease. Thus, one must consider an algorithm that accounts for the variable nature of the disease presentation. The goal of such an algorithm is the accurate identification and staging of the disease. For disease not roentgenographically apparent, an approach using magnetic resonance imaging and bone scanning is recommended. For disease that is apparent roentgenographically, tomography is used to define the extent of the disease and the presence or absence of subchondral fracture. The accuracy of diagnosis is critical to understanding the role of the various treatment modalities prescribed for ON. For this purpose, it is necessary to reach a consensus as to what constitutes a successful outcome of treatment. Once diagnosis of the disease is accepted, clinical success of treatment outcomes should be reported in three ways: by a standard hip rating system, by ability to prevent roentgenographic deterioration, and by survival of the femoral head (the absence of further treatment intervention).(ABSTRACT TRUNCATED AT 250 WORDS)

Antithrombin III/low-dose heparin in the prevention of deep-vein thrombosis after total knee arthroplasty. A preliminary report

This preliminary report outlines the rationale for a new approach to deep-vein thrombosis (DVT) prophylaxis in total knee arthroplasty (TKA) patients and describes preliminary hematologic and venographic findings. A protocol was employed to (1) document a series of hematologic events surrounding cemented TKA and the alterations of these events by the study drugs and (2) compare the safety and efficacy of a regimen of antithrombin III/low-dose heparin (ATIII/LDH) to that of low-molecular-weight dextran (LMWD) in the prevention of DVT after TKA. Using a dosage regimen of 3000 units of ATIII as a loading dose followed postoperatively by 2000 units daily combined with 5000 units of LDH twice daily, a prospective randomized study of patients treated by cemented TKA was performed. The ATIII/LDH regimen was compared with LMWD (10 ml/kg x 12 hours loading dose followed by 7 ml/kg x 24 hours maintenance dose). The rate of DVT after TKA in 42 patients was 25% (5/20) for the ATIII/LDH group versus 82% (18/22) for the LMWD group (p less than 0.001). Bleeding complications were minimal and comparable for each group. Hematologic studies demonstrated that quantitative and functional ATIII levels decreased after TKA and that preoperative loading with ATIII prevented levels from falling below 100%. Studies of clot formation (fibrinopeptide A) and plasmin activity (fibrinopeptides B beta 15-42 and 1-42) in 34 patients suggest some reduction in procoagulant activity in patients in the ATIII/LDH group. These findings indicate that the combination of ATIII and LDH may offer superior protection from DVT than does LMWD.

Management of orthopedic complications of metabolic bone disease

Orthopedic manifestations of metabolic bone disease are usually related to structural compromise of the skeleton. Fractures due to osteoporosis are the most often encountered problem. In this overview, the authors focus on the commonly encountered fractures related to osteoporosis and discuss concerns and complications related to their management. In addition, they point out the subtle ways in which less commonly encountered metabolic bone diseases, such as osteomalacia, hyperparathyroidism, and Paget's disease, might come to the attention of the orthopedist. Appropriate criteria for medical and surgical management are suggested.

Multimodality approach to osteonecrosis of the femoral head

Treatment of osteonecrosis of the femoral head appears to be effective when the disease is identified and treated early. Forty-one patients were evaluated with prospective laboratory assessment, anteroposterior and frog-lateral roentgenograms of both hips, intraosseous pressure measurements (IOP), magnetic resonance imaging (MRI), and 99mTc methylene diphosphonate planar and single-photon emission computerized tomographic (SPECT) bone imaging. Pathologic specimens were obtained in most patients. Preradiographic disease was identified in 26 hips and 11 of these were asymptomatic. Fifteen clinically symptomatic hips had normal plain roentgenograms, but abnormal protocol studies. Evaluation of sensitivity, specificity, and predictive value (positive and negative), respectively, in diagnosing osteonecrosis of the femoral head revealed the following percentages: 83%, 83%, 96%, and 48% for planar bone scanning; 91%, 78%, 94%, and 70% for SPECT; 87%, 83%, 96%, and 55% for MRI; 80%, 60%, 95%, and 25% for IOP; and 88%, 100%, 100%, and 25% for core biopsy. (There were few true negatives, thus specificity values are approximations.) The identification of preradiographic stages is possible, but difficult. MRI appears appealing at present, particularly in identifying disease in asymptomatic hips. However, there is no definitive method for noninvasive diagnosis. Pathologic confirmation in early stages is difficult.