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Aseptic tibial loosening following primary total knee arthroplasty persists despite technique and device-related advancements. The mechanisms for this mode of failure are not well understood. We hypothesized that knee movement while the cement was curing dispersed lipids at the implant-cement interface and would result in decreased tibial fixation strength.A cadaveric study was performed utilizing 32 torso-to-toe specimens (64 knees). Four contemporary total knee arthroplasty designs were evaluated. Each implant design was randomly assigned to a cadaveric specimen pair with side-to-side randomization. Specimen densitometry was recorded. Each tibial implant was cemented using a standard technique. On one side, the tibial component was held without motion following impaction until complete cement polymerization. The contralateral knee tibial implant was taken through gentle range of motion and stability assessment 7 minutes after cement mixing. Axial tibial pull-out strength and interface failure examination was performed on each specimen.The average pull-out strength for the no motion cohort (5,462 N) exceeded the motion cohort (4,473 N) (P = .001). The mean pull-out strength between implant designs in the no motion cohort varied significantly (implant A: 7,230 N, B: 5,806 N, C: 5,325 N, D 3,486 N; P = .007). Similarly, the motion cohort inter-implant variance was significant (P ≤ .001). Intra-implant pull-out strength was significantly higher in implant A than D. The average pull-out strength was significantly lower in specimens that failed at the implant-cement interface vs bone failures (4,089 ± 2,158 N vs 5,960 ± 2,010 N, P.0025).Knee motion during cement polymerization is associated with significant decreases in tibial implant fixational strength. Reduction in implant pull-out strength was identified with each implant design with motion and varied between designs. Across all tested designs, we recommend limiting motion while cementing the tibial implant to improve fixation strength.

Introduction Aseptic tibial loosening is now considered the most common reason that total knee arthroplasties (TKA) fail long-term. There are unique subsets of patients that fail into varus alignment of the tibial tray with collapse of the medial proximal tibia. In these patients with varus collapse of the tibia, there is a combination of medial tibial bone collapse and tibial implant loosening. However, it is currently unknown if the implant fixation fails first or if the proximal medial tibia collapses first. Therefore, the following study was designed to answer this question. Materials We performed a retrospective analysis of 88 patients that were revised at our institution secondary to aseptic varus collapse of the proximal tibia. Two fellowship trained Arthroplasty surgeons performed a retrospective analysis on a series of precollapse radiographs in each patient to determine which failed first: the implant fixation (implant-cement or cement-bone interface) or the medial proximal tibia. Discussion 36/88 (40.9%) patients had a series of precollapse radiographs that could be reviewed. Reviewer one identified 23 (63.9%) patients with radiographic evidence of failure at the implant-cement interface before varus collapse, two (5.6%) patients had a mixed pattern of failure at the implant-cement and cement-bone interface before varus collapse, and 11 (30.6%) patients had contemporaneous failure at the implant-cement interface and varus collapse of the proximal tibia. Reviewer two identified 22 (61.1%) at the implant-cement interface, two (5.6%) with a mixed pattern, and 12 (33.3%) with contemporaneous failure and varus collapse. Conclusion The most frequent mechanism of failure identified was failure of the implant-cement interface followed by subsequent medial tibial varus collapse. Improving implant fixation may decrease the incidence of this unique failure mechanism. We advocate the use of supplemental stem fixation in high-risk patients and optimal cement techniques for all patients as methods of potentially avoiding tibial varus collapse, and subsequent bone loss.

Dislocation remains the leading indication for revision of total hip arthroplasty (THA). The objective of this study was to use a computational model to compare the overall resistance to both anterior and posterior dislocation for the available THA constructs commonly considered by surgeons attempting to produce a stable joint. Patient-specific musculoskeletal models of THA patients performing activities consistent with anterior and posterior dislocation were developed to calculate joint contact forces and joint positions used for simulations of dislocation in a finite element model of the implanted hip that included an experimentally calibrated hip capsule representation. Dislocations were then performed with consideration of offset using +5 and +9 offset, iteratively with three lipped liner variations in jump distance (10°, 15°, and 20° lips), a size 40 head, and a dual-mobility construct. Dislocation resistance was quantified as the moment required to dislocate the hip and the integral of the moment-flexion angle (dislocation energy). Increasing head diameter increased resistive moment on average for anterior and posterior dislocation by 22% relative to a neutral configuration. A lipped liner resulted in increases in the resistive moment to posterior dislocation of 9%, 19%, and 47% for 10°, 15°, and 20° lips, a sensitivity of approximately 2.8 Nm/mm of additional jump distance. A dual-mobility acetabular design resulted in an average 38% increase in resistive moment and 92% increase in dislocation energy for anterior and posterior dislocation. A quantitative understanding of tradeoffs in the dislocation risk inherent to THA construct options is valuable in supporting surgical decision making.

Background In total hip arthroplasty (THA), component position is critical to avoid instability and improve longevity. Appropriate combined femoral and acetabular component anteversion is important for improved THA stability and increased impingement-free range of motion. In direct anterior THA (DA-THA), concern has been expressed regarding the accuracy of femoral component positioning. This study seeks to quantify acetabular, femoral, and combined component orientation relative to the accepted “safe zones” in patients who have undergone DA-THA. Methods Twenty-nine patients who had THA performed via direct anterior approach had postoperative computerized tomography scans done to assess femoral anteversion. Stem rotational alignment was measured relative to the transepicondylar axis (TEA) and the posterior condylar axis (PCA) of the femur at the knee. Acetabular abduction and version were recorded on anteroposterior pelvis radiographs. Results The mean stem anteversion was 17.5° (standard deviation = 10.8°) from the TEA and 21.7° (standard deviation = 11.3°) from the PCA. Ten of 30 cups were appropriately anteverted; however, all the cups had appropriate abduction. Combined version when using the TEA resulted in 79% (23/29) of patients within the “safe zone” of 25°-50°. Pearson correlation coefficients were high for both stem anteversion from the TEA (R = 0.96) and PCA (R = 0.98); however, interobserver reliability for combined component anteversion was greater for the TEA (kappa, 0.83 vs 0.65). Conclusions Combined anteversion within the “safe zone” was achieved 79% of the time with DA-THA. Interestingly, most of the “excessive” combined anteversion appears to be related to increased anteversion of the acetabular component with only 10 patients within the acetabular cup “safe zone” of 5°-25°.

Aseptic tibial loosening following primary total knee replacement is one of the leading causes of long-term failure. Cement mantle thickness has been implicated as a source of aseptic tibial loosening. Therefore, the following study was designed to determine (1) what is the cement mantle thickness in patients that develop aseptic tibial loosening, and (2) is there a difference in cement mantle thickness based on the interface of failure?This retrospective cohort included 216 patients revised for aseptic tibial loosening. Patient demographics, operative data, and clinical outcomes were recorded. A preoperative radiographic assessment was performed to determine the interface of failure and the thickness of the cement mantle using the Knee Society Radiographic Evaluation System zones.The average patient age was 65 years and body mass index was 33.7 kg/mPatients that develop implant loosening at the cement-bone interface were noted to have a significantly decreased cement mantle compared to patients that failed at the implant-cement interface. Methods for decreasing tibial implant loosening should likely focus on improving the fixation at the implant-cement interface.

Corticosteroids are commonly used intraoperatively to treat pain and reduce opioid consumption and nausea associated with primary total joint arthroplasty (TJA). The purpose of this study was to evaluate the efficacy and safety of corticosteroids in primary TJA to support the combined clinical practice guidelines of the American Association of Hip and Knee Surgeons, American Academy of Orthopaedic Surgeons, Hip Society, Knee Society, and the American Society of Regional Anesthesia and Pain Management.The MEDLINE, Embase, and Cochrane Central Register of Controlled Trials databases were searched for studies published before February 2020 on corticosteroids in TJA. All included studies underwent qualitative and quantitative homogeneity testing followed by a systematic review and direct comparison meta-analysis to assess the efficacy and safety of corticosteroids.Critical appraisal of 1,581 publications revealed 23 studies regarded as the best available evidence for analysis. Intraoperative dexamethasone reduces postoperative pain, opioid consumption, and nausea and vomiting. Multiple doses lead to further reduction in pain, opioid consumption, nausea and vomiting. There is insufficient evidence on the risk of adverse events with perioperative dexamethasone in TJA.Strong evidence supports the use of a single dose or multiple doses of intravenous dexamethasone to reduce postoperative pain, opioid consumption, nausea and vomiting after primary TJA. There is insufficient evidence on perioperative dexamethasone in primary TJA to determine the optimal dose, number of doses, or risk of postoperative adverse events.

Background Aseptic tibial loosening is a frequent cause of long-term failure following primary cemented total knee replacement. Failure of the tibial implant can occur at the implant-cement interface or at the cement-bone interface. Currently, it is unknown at which interface failure occurs in cases of aseptic tibial loosening. The following study was designed to determine which interface represents the “weak link” for tibial implant fixation. Methods We performed a retrospective analysis of 149 patients who were revised secondary to aseptic tibial loosening at our institution from 2005 to 2017. Operative reports and radiographs were reviewed on each patient to determine the location and pattern of fixation failure. Results Implant failure was more prevalent at the implant-cement than cement-bone interface, 140/149 (94.0%) vs 9/149 (6.0%). Additionally, we noted 2 distinct patterns of failure in patients that loosened at the implant-cement interface. Ninety of 140 (64.3%) patients developed varus collapse pattern of failure. Forty-nine of 140 (35.0%) patients developed failure between the implant-cement interface without angulation. All 149 patients had heterotopic bone formation anterior to the tibial baseplate, which was consistent regardless of which interface failed. Conclusion The most frequent interface failure identified in our study was at the implant-cement interface, 140/149 (94.0%). This finding has substantial clinical ramifications. Because failure was predominantly at the implant-cement interface there may be design opportunities for increasing implant fixation to cement. Implants with improved undersurface tibial tray features may be necessary to mitigate the risk of failure at this interface, especially in overly active patients or those with elevated body mass indices.

In an era of innovation in surgical approaches for total hip arthroplasty (THA), there is concern for increasing trends of early failure. The purpose of this study is to evaluate the incidence of early failure of primary THA stratified by surgical approach.A retrospective review was performed on consecutive primary THAs completed from 2007 to 2014 at a high-volume center. THAs were stratified by surgical approach. Only the direct anterior (DAA) and posterior approaches (PA) were included. The primary outcome measure was early revision (5 years). Descriptive statistics were performed using SAS software.In total, 6894 primary THAs performed between 2007 and 2014 were included. Across 2431 DAA THAs and 4463 PA THAs, there were 103 revisions overall. There was no difference in the overall revision rate for DAA THAs (1.69%) compared to PA THAs (1.39%) (P = .33). The DAA had a higher rate of early revisions for femoral component loosening compared to the PA (P = .0003). About 35.7% of DAA THAs were revised for femoral loosening compared to 8% for the PA (P = .0003). Early failure by femoral loosening occurred more often via the DAA in Dorr A bone (P = .03). The PA had a higher incidence of revision for instability (P = .04). There was no difference in modes of failure with regards to time to failure, acetabular loosening, early periprosthetic fracture, or infection.The DAA had a higher incidence of femoral loosening while PA had a higher mode of failure due to instability. Overall revision rates were not statistically different between approaches.

Consensus regarding femoral stem fixation options in revision total knee arthroplasty remains controversial. Tapered, modular, fluted titanium (TMFT) stems have an excellent track record in total hip arthroplasty for their ability to provide axial and rotational stability in situations of compromised host bone. We present 3 successfully treated cases in which the Food & Drug Administration granted permission to use custom TMFT stems in situations of failed femoral fixation in multiple revised knees. These stems hold promise to achieve stable fixation in revision total knee arthroplasty where host metadiaphyseal bone is deficient. Implant manufactures should consider dedicating future resources to create adapters that can link existing successful TMFT stems currently used in hip arthroplasty to revision total knee components when host bone is severely compromised.

Background Intraoperative periarticular injections (PAIs) with local anesthetic are an important component of multimodal pain control in total joint arthroplasty. Liposomal bupivacaine is an extended-release formulation of bupivacaine designed to provide extended pain relief, approved for use in a single surgical site. The systemic safety profile for use in simultaneous bilateral TKA (bTKA) with a full dose in each knee has not been evaluated. The purpose of this study was to determine the safety and pharmacokinetics of bilateral full-dose PAI liposomal bupivacaine in the blood collected in patients undergoing simultaneous bTKA. Methods In this prospective study, patients had an identical PAI consisting of 20 cc of liposomal bupivacaine (266 mg), 30 cc of 0.25% bupivacaine (75 mg) with epinephrine, and 10 cc of normal saline injected into each knee during bTKA. Blood samples were collected at predefined intervals until patient discharge. No exogenous bupivacaine was administered. Pharmacokinetic evaluations were subsequently performed and compared to bupivacaine toxicity levels. Patients were monitored for adverse events related to anesthetic toxicity (cardiac and neurologic). Results Fifteen patients (mean age, 60.7 years; range, 57-64 years) were enrolled in the study. The mean peak level (Cmax) was 0.8 μg/mL (range, 0.4-1.2 μg/mL). All patients were well below the reported systemic cardiac and toxicity levels reported as 2-4 μg/mL. There were no reported cardiac and neurotoxic events in any patients. Conclusion The use of full-dose PAI with liposomal bupivacaine placed into each knee during simultaneous bTKA is safe with systemic bupivacaine levels well below reported cardiac and neurotoxic levels.

Acetabular implant revision is commonly performed during revision total hip arthroplasty (THA).

Background Posterior-stabilized total knee arthroplasty (TKA) with gradually variable radii (G-curve) femoral condylar geometry is now available. It is believed that a G-curve design would lead to more mid-flexion stability leading to reduced incidence of paradoxical anterior slide. The objective of this study was to assess the in vivo kinematics for subjects implanted with this type of TKA under various conditions of daily living. Methods Tibiofemoral kinematics of 35 patients having posterior-stabilized TKA with G-curve design were analyzed using fluoroscopy while performing three activities: weight-bearing deep knee bend, gait, and walking down a ramp. The subjects were assessed for range of motion, condylar translation, axial rotation, cam-spine engagement, and condylar lift-off. Results The average weight-bearing flexion during deep knee bend was 111.4°. On average, the subjects exhibited 5.4 mm of posterior rollback of the lateral condyle and 2.0 mm of the medial condyle from full extension to maximum knee flexion. The femur consistently rotated externally with flexion, and the average axial rotation was 5.2°. Overall movement of the condyles during gait and ramp-down activity was small. No incidence of condylar lift-off was observed. Conclusion Subjects in this study experienced consistent magnitudes of posterior femoral rollback and external rotation of the femur with weight-bearing flexion. The variation is similar to that previously reported for normal knee where the lateral condyle moves consistently posterior compared to the medial condyle. Subjects experienced low overall mid-flexion paradoxical anterior sliding and no incidence of condylar lift-off leading to mid-flexion stability.

This study sought to prospectively examine the clinical and radiographic differences between direct anterior (DA-THA) and mini-posterior approach total hip arthroplasty (MPA-THA). Fifty-four patients were prospectively randomized to either MPA or DA-THA. Patient recorded diaries were collected. Radiographs were reviewed. SF-36, WOMAC and HHS scores were tabulated. Time to ambulation without any assistive device favored DA-THA (22 vs. 28 days, P=0.04). Three week SF mental scores favored MPA-THA (60.66 vs. 58.43, P=0.01). In a randomized prospective trial, patients undergoing DA-THA voluntarily quit use of all walking aids on average 6 days earlier than patients with a MPA-THA. Little additional clinical or radiographic benefit was seen between the cohorts.

Patient specific instrumentation (PSI) was developed to increase total knee arthroplasty (TKA) accuracy and efficiency. The study purpose was to compare immediate post-operative mechanical alignment, achieved using PSI, with conventional and computer assisted surgery (CAS) instruments in high volume TKA practices. This prospective, multicenter, non-randomized study accrued 66 TKA patients using PSI. A computed tomography (CT) based algorithm was used to develop the surgical plan. Sixty-two percent were females, 99% were diagnosed with osteoarthritis, average age at surgery was 66 years, and 33 was the average body mass index. A historical control group was utilized that underwent TKA using conventional instruments (n=86) or CAS (n=81), by the same set of surgeons. Postoperative mechanical alignment was comparable across the groups. Operative time mean and variance were significant.

Liaison: Paul Lichstein MD, MSLeaders: Thorsten Gehrke MD (International), Adolph Lombardi MD, FACS (US),Carlo Romano MD (International), Ian Stockley MB, ChB, MD, FRCS (International)Delegates: GeorgeBabisMD,JerzyBialeckiMD,LaszloBucsiMD,XuCaiMD,LiCaoMD,BriandeBeaubienMD,Johannes Erhardt MD, Stuart Goodman MD, PhD, FRCSC, FACS, FBSE, William Jiranek MD,PeterKeoghFRCSI,DavidLewallenMD,MS,PaulMannerMD,WojciechMarczynskiMD,J.BohannonMasonMD,Kevin Mulhall MB, MCh, FRCSI, Wayne Paprosky MD, Preetesh Patel MD, Francisco Piccaluga MD,Gregory Polkowski MD, Luis Pulido MD, Ian Stockley MBBS, ChB, FRCS, Juan Suarez MD, Fritz Thorey MD,Rashid Tikhilov MD, Job Diego Velazquez MD, Heinz Winkler MD

Liaison: Paul Lichstein MD, MSLeaders: Thorsten Gehrke MD (International), Adolph Lombardi MD, FACS (US), Carlo RomanoMD (International), Ian Stockley MB, ChB, MD, FRCS (International)Delegates: George Babis MD, Jerzy Bialecki MD, La´szlo´ Bucsi MD, Xu Cai MD, Li Cao MD, Briande Beaubien MD, Johannes Erhardt MD, Stuart Goodman MD, PhD, FRCSC, FACS, FBSE,William Jiranek MD, Peter Keogh, David Lewallen MD, MS, Paul Manner MD, WojciechMarczynski MD, J. Bohannon Mason MD, Kevin Mulhall MB, MCh, FRCSI, Wayne PaproskyMD, Preetesh Patel MD, Francisco Piccaluga MD, Gregory Polkowski MD, Luis Pulido MD, IanStockley MBBS, ChB, FRCS, Juan Suarez MD, Fritz Thorey MD, Rashid Tikhilov MD, JobDiego Velazquez MD, Heinz Winkler MD

The adoption and utilization of the direct anterior approach (DAA) for total hip arthroplasty (THA) has increased significantly over the past decade. This review presents the available literature for early recovery and outcomes of the DAA THA. A growing body of evidence points towards superior early recovery and early functional outcomes with the DAA in experienced hands compared to posterior and lateral based approaches in regards to pain, opioid use, length of stay, and early markers of mobility. In an era of rapid recovery protocols, the DAA with its early pain and functional advantages can effectively deliver safe and effective value for the total hip population.

The study purpose was to analyze current results of modern cementless femoral components in young patients having total hip arthroplasty (THA) or hip resurfacing. Twenty-two studies (n = 5907; hips = 6408) evaluating modern cementless THA in young patients and 15 studies evaluating hip resurfacing (n = 3002; hips = 3269) were included. Meta-analysis techniques were used to pool failure rates. The pooled failure rate for THA using femoral revision for mechanical failure as an end point was 1.3% (95% confidence interval [CI], 1.0%-1.7%) at a mean 8.4 years of follow-up. At a mean of 3.9 years of follow-up, the pooled mechanical failure rate of the femoral component for hip resurfacing was 2.6% (95% CI, 2.0-3.4). In conclusion, the enthusiasm for hip resurfacing should be tempered by these data. Longer follow-up and direct comparison trials are required to confirm these findings.

Computer-assisted surgery (CAS) has been advocated as a means to improve limb and prosthesis alignment and assist in ligament balancing in total knee arthroplasty (TKA). Thus, we sought to examine alignment outcomes in CAS vs conventional TKA. A systematic review of literature from 1990 to 2007 was performed. Direct comparison of alignment outcomes was performed using random effects meta-analyses. Twenty-nine studies of CAS vs conventional TKA were identified, and included mechanical axis malalignment of greater than 3 degrees occurred in 9.0% of CAS vs 31.8% of conventional TKA patients. The risk of greater than 3 degrees malalignment was significantly less with CAS than conventional techniques for mechanical axis and frontal plane femoral and tibial component alignment. Tibial and femoral slope both showed statistical significance in favor of CAS at greater than 2 degrees malalignment. Meta-analysis of alignment outcomes for CAS vs conventional TKA indicates significant improvement in component orientation and mechanical axis when CAS is used.

A retrospective review of patients with joint arthroplasty was performed to determine if body mass index has increased with time and if the body mass index of patients with arthroplasty was significantly different than that of the general population. We also sought to determine if reimbursement kept pace with this growing cohort. The number of obese patients increased from 30.4% in 1990 to 52.1% in 2005 (P < .0001). In 2005, 24% of the general population was obese, whereas 52.1% of arthroplasty patients were obese. Physician reimbursement decreased 38% for knee arthroplasty and 46% for hip arthroplasty and the need for total joint arthroplasty because of these confounding variables will increase exponentially beyond scheduled expectations. Patients and health policy forecasters must understand the interrelationship between obesity and the need for arthroplasty.

Utilization of the direct anterior approach (DAA) for total hip arthroplasty (THA) has increased in the last decade with fluoroscopy often used to confirm implant position, leg length, and offset. Radiation exposure thresholds around 800 mGy are published for the risk of cataracts. We hypothesized that surgeon eye exposure during fluoro-assisted DAA total hip arthroplasty would be well below these published thresholds.Three experienced orthopedic surgeons performed 30 consecutive fluoro-assisted DAA THAs. During each procedure, the surgeon wore a helmet-mounted dosimeter. After 30 consecutive cases, the dosimeters were analyzed. A chart review was then completed to obtain fluoroscopic data saved for each individual case including fluoroscopic time, total radiation dose, and radiation tech experience.Fluoroscopic data were available for 89 of 90 cases (98.8%). Surgeon 1 had an average fluoroscopic time of 18.51 seconds, radiation dose of 2.396 mGy, and tech experience of 13.06 years. Surgeon 2 had an average fluoroscopic time of 15.63 seconds, radiation dose of 2.139 mGy, and tech experience of 23.69 years. Surgeon 3 had an average fluoroscopic time of 11.06 seconds, radiation dose of 1.462 mGy, and tech experience of 16.03 years. The dosimeter results were 8, 5, and1 mrem, respectively, for each surgeon. The mean total radiation dose per case for all surgeons was 2.00 mGy (±1.31), and there was no correlation between radiation dose and radiologic tech experience (0.089, P.05) or radiation dose and patients' body mass index (0.260, P = .014).Each surgeon would need to perform300,000 DAA THAs to exceed the 800-mGy cataract threshold dose. The decision to wear protective glasses should be at the surgeon's discretion; however, the findings in this study show a very low radiation dose to the surgeon's eye regardless of radiologic tech experience or patient's body mass index.

We conducted a randomized controlled trial to compare efficacy of an occlusive antimicrobial barrier dressing and a standard surgical dressing in patients who underwent primary total joint arthroplasty. Two hundred sixty-two patients were randomized to receive either an occlusive dressing or a standard dressing. Wounds were closed in identical fashion. Outcomes included wound complications, dressing changes, and patient satisfaction. With use of occlusive dressing (vs standard dressing), wound complications (including skin blistering) were significantly (P = 0.15) reduced; there were significantly (P.0001) fewer dressing changes; and patient satisfaction was significantly (P.0001) higher. Use of occlusive dressings can reduce wound complications and promote wound healing after total joint arthroplasty.

Acetabular component deformation secondary to forces encountered during insertion is a potential consequence of the press-fit technique. This study characterized the stiffness of Pinnacle 100 cups (DePuy, Warsaw, Ind) via mechanical testing and used this information with intraoperative measurements of cup deformation to calculate the in vivo forces acting on cups inserted during hip arthroplasty in 21 patients. We found that 90.5% of cups had measurable compression deformity, averaging 0.16 +/- 0.16 mm. The corresponding forces acting on these cups averaged 414 +/- 421 N. For hard-on-hard bearing surfaces, such in vivo deformation of acetabular shells may result in negative clinical consequences such as equatorial loading with increased wear and potential seizing of components, chipping of ceramic inserts, or locking mechanism damage.

UNLABELLED Revision total knee arthroplasty requires the removal of one or all of the prior knee components. Thoughtful and careful removal of well-fixed total knee components can preserve host bone stock and facilitate subsequent reconstructive efforts. The tools and techniques for knee component removal include simple osteotomes, saws, extraction devices, ultrasonic devices, and frequently a combination of some or all of the above. It is the unique nature of each revision arthroplasty, which presents the surgeon with such challenge. Each of the techniques discussed in this review reflects the anecdotal experience acquired in over 800 revision total knee arthroplasties performed at our center. We review our empiric bias regarding the individual applicability of these techniques. LEVEL OF EVIDENCE Therapeutic studies, Level V (expert opinion). See Guidelines for Authors for a complete description of Levels of Evidence.

UNLABELLED We compare the clinical and radiographic results of partial-component versus full-component revision total knee arthroplasty. A retrospective review was used to identify patients who had partial revision total knee arthroplasty. Only isolated femoral or tibial revisions were included. From 1986 to 2000, 448 revision total knee arthroplasties were done. Seventy-seven partial revisions were done. Three were excluded for a diagnosis of infection. The average followup was 63 months. The average Knee Society score for full component revisions was 85 compared with 79 for partial revisions. This difference was significant (p = 0.0001). The average Knee Society score for those patients who had a full revision for instability was 85 compared with 63 for partial revision (p = 0.0001). The average Knee Society score for those patients who had a full revision for wear-related problems was 88 compared with 78 for partial revisions (p = 0.03). Although the advantages of partial revision in hip replacement are well-documented, the efficacy of this treatment strategy has not been established in revision total knee arthroplasty. Care should be taken when considering partial revision for instability or wear-related problems. LEVEL OF EVIDENCE Therapeutic study, Level III (retrospective cohort study). See the Guidelines for Authors for a complete description of levels of evidence.

The appropriate treatment for the young patient with post-collapse avascular necrosis (AVN) of the femoral head continues to be controversial. Femoral surface replacement (FSR) has emerged as a potential strategy to delay total hip arthroplasty in these patients. Between 1997 and 2003, 37 FSR procedures were performed. Success was defined as patients not requiring revision surgery or having a Harris hip pain score of 30 or greater. Failure was defined as patients having revision surgery or a Harris hip pain score of 20 or less. The overall failure rate based on Harris hip pain scores and revision surgery was 64.8% (24/37 procedures). Fifteen (40.5%) procedures required revision surgery, whereas 9 (24.3%) patients were considered failures based on their pain scores. The purpose of this study was to determine if FSR is a viable option for post-collapse AVN. We conclude that hemiresurfacing for AVN is an unpredictable procedure. This procedure is no longer offered as a treatment option for post-collapse AVN at our institution.

This study evaluates the difficult reconstructive challenge of severe proximal femoral bone loss. We present intermediate-term results of 46 hips with extensive proximal femoral bone loss that underwent revision total hip arthroplasty using cementless distal fixation without supplemental allograft. All were evaluated with the Harris hip score at a minimum of 2 years. Radiographs were assessed using the Engh fixation scale. At a mean of 6.4 (range 2-12) years, 43 of the 46 prostheses were functioning well. Two patients required revision for symptomatic loosening, and 1 prosthesis remains radiographically loose with a fair clinical score. Mean Harris hip score was 77 at last follow-up. There were 6 intraoperative femur fractures, 9 dislocations, 10 cases of severe stress shielding, and no infections.

M inimally invasive hip surgery techniques have been advocated as an alternative to total hip arthroplasty performed with conventional soft-tissue exposure. Purported advantages of the minimally invasive technique have included faster functional recovery, a shorter stay in the hospital, less blood loss, and an improved cosmetic result1. Any new surgical technique involves a learning curve. The steepness of this curve and the true complication rates cannot be established until these procedures have been performed by surgeons other than those who champion the technique. Ideally, before any new procedure is adopted for widespread use, prospective, controlled, multicenter studies should prove the procedure's safety and efficacy. Recently, three patients with catastrophic complications of minimally invasive hip replacement were referred to our tertiary total joint revision center. Each arthroplasty had been performed by a different orthopaedic surgeon who stated, in his operative note, that a minimally invasive approach had been used. Two of the patients consented to have data concerning the case submitted for publication, whereas the third patient died in the recovery room after being directly transferred from an outside clinic to our hospital. Thus, she did not sign the release form at the clinic. C ase 1. A sixty-seven-year-old woman underwent a primary total hip arthroplasty that was performed with use of minimally invasive techniques at another institution. The patient was 5 ft and 6 in (167.6 cm) tall and weighed 180 lb (81.6 kg). The procedure was performed through a 9-cm incision. During the operation, difficulty with reaming of the acetabulum was encountered and a segmental defect in the superior dome of the acetabulum was created. The defect was recognized intraoperatively, but no suitable revision components were available and the surgeon called our institution requesting transfer of the patient to our care. Two days after admission to our …

Between 1986 and 1998, 81 total hip revisions were performed for recurrent instability. Twenty-three revisions were fixed cups to bipolars. Average follow-up was 50 months. Radiographic evaluation showed no significant osteolysis and average migration of 1.7 mm. The average postoperative Harris hip score was 74. All patients who underwent revision to a bipolar prosthesis had no further instability. Acetabular revision to a bipolar prosthesis provides stability in recurrent prosthetic hip instability.

Osteolysis is perhaps the biggest unsolved problem in joint arthroplasty. Many factors contribute to osteolysis, some of which cannot be controlled. It is imperative to minimize controllable factors contributing to osteolysis whenever possible. We report four cases of trunion impingement on an elevated rim liner, which may have contributed to early aggressive osteolysis. Although the use of an elevated liner may result in a lower incidence of postoperative instability, the trade-off in using such a device must be understood.

A white blood cell count (WBC) of >50000 cell/mm(3) from a knee aspirate with >or=80% polymorphonuclear cells (PMNCs) is suggestive of infection. This study sought to determine if these same criteria were applicable when interpreting aspirates from a total knee. Of 440 revision total knee arthroplasties, 86 patients had preoperative aspirations of the knee before revision. Fifty-five aspirates were from aseptic failures; 31 aspirates were from patients determined to have septic failure. The mean white blood cell (WBC) count in aspirates from the aseptic group was 645 cells/mm(3) (SD = 878). The mean WBC count in the septic group was 25951 cells/mm(3) (SD = 34994; P=

Methods of stem fixation are a controversial aspect of revision TKA. We sought to determine which technique was superior by reviewing 475 revision TKAs done between 1986 and 2000. Of these 475 revisions, 286 major component revisions were done using 484 extended stems for fixation. Patients who died, patients who had less than 2 years follow up, or patients who had diaphyseal engaging stems were excluded from the study. The final data set included 113 revision TKAs with 202 metaphyseal engaging stems. Of the 202 stems, 107 were cemented whereas 95 were press-fit metaphyseal engaging stems. One hundred one of these were femoral stems and 101 were tibial stems. Using a modified Knee Society radiographic scoring system, 100 (93%) of the 107 implants with cemented stems were considered stable, seven (7%) were categorized as possibly loose requiring close followup, and none were loose. Of the 95 implants placed with cementless stems, only 67 (71%) were categorized as stable. Eighteen (19%) were possibly loose requiring close followup and 10 (10%) were loose (two tibial and eight femoral implants). We currently would urge caution in using cementless metaphyseal engaging stems for fixation in revision TKA.

The hip joint is the most deeply recessed joint in the body, making it difficult to access arthroscopically. Thelateral position facilitates peritrochanteric approaches, which provide reproducible bony landmarks for orientation, as well as access for most pathology within the hip joint. Minimally invasive approaches to the hip joint have been developed for situations where open techniques are less advantageous, such as the patient with a symptomatic loose body or labral tear. The different portals have varying abilities to visualize different anatomic structures. Knowledge of anatomic relationships is of utmost importance in the use of the various portals. Meticulous attention to proper positioning, adequate joint distraction, and portal placement is paramount for safe and successful arthroscopy of the hip. This article will review the seminal features of lateral positioning and minimally invasive surgical approaches to the hip.

Hip instability is the leading cause of morbidity after total hip arthroplasty. Surgical strategies that have been used to eliminate recurrent instability include component revision, trochanteric advancement, or the use of constrained components. Between 1986 and 1997, 731 revision total hip arthroplasties were performed at our institution. A total of 29 patients underwent modular component exchange to treat hip instability. After revision surgery, 16 of 29 (55%) patients experienced redislocation. Nine (31% overall) patients dislocated repeatedly after modular component exchange. Five of the 9 patients who dislocated repeatedly (17% overall) ultimately required rerevision to obtain stability. Modular component exchange is an unpredictable procedure in definitively solving hip stability problems. The limitations of this procedure in treating this complex multifactorial problem must be understood by patient and surgeon alike. Copyright 2002, Elsevier Science (USA). All rights reserved.

Satisfactory performance of revision total knee arthroplasty (TKA) requires adequate exposure. This article shows the patella inversion method of exposure in a large consecutive series of revision TKAs.Between 1987 and 1999, 420 revision TKAs were performed. Exposure was facilitated by the patella inversion method. No attempt was made to evert the patella. This technique of exposure was used in 95% (397 of 420) of patients. There were no episodes of patellar tendon avulsion in this series. Multiple exposure options are available in revision TKA. Extensile techniques violate the extensor mechanism. For most patients, these methods were unnecessary. The patella inversion method afforded adequate exposure in most patients without violating the extensor mechanism.

Posterolateral and anterolateral approach THA disrupts femoral vessel blood flow, however, this has not been established for the direct anterior (DA) approach. Ten patients undergoing primary DA THA had peak vascular flow rates for the femoral artery and vein calculated via Doppler ultrasound at specified points: incision, acetabular preparation, femoral preparation and final reduction. Peak femoral arterial and venous flow decreased over baseline, but not significantly, during acetabular preparation (P=0.88, P=0.98) and femoral preparation (P=0.97, P=0.97). At final reduction, arterial peak flow was restored (P=1) with an increase in venous flow (P=0.55). Although there were alterations to peak flow, no vessel occlusion occurred at any point during DA THA.