Nicholas M. Brown

Total Knee Arthroplasty Has Higher Postoperative Morbidity Than Unicompartmental Knee Arthroplasty: A Multicenter Analysis

A total of 2235 primary total knee arthroplasties (TKAs) and 605 unicompartmental knee arthroplasties performed at 3 institutions over 5 years were reviewed to compare the incidence of postoperative complications between these groups. The overall risk of complications for patients undergoing TKA was 11.0%, compared with 4.3% for patients undergoing unicompartmental knee arthroplasty (P < .0001). Total knee arthroplasty was associated with increased rates of manipulation (odds ratio [OR], 13.0; P < .0001), transfusion (OR, 8.5; P = .036), intensive care unit admission (OR, 7.4; P = .049), discharge to a rehabilitation facility (OR, 5.2; P < .0001) and had longer hospital stays (mean, 3.3 vs 2.0 days; P < .0001). There was a trend toward an increased risk of deep infection (0.8% vs 0.2%, P = .13), readmission (4.2% vs 2.7%, P = .0795), thromboembolic events (1.0% vs 0.64%, P = .398), and any reoperation (1.4% vs 0.6%; P = .064). The increased risk of perioperative complications after TKA should be considered when counseling patients if they are an appropriate candidate for either procedure.

Serum and Synovial Fluid Analysis for Diagnosing Chronic Periprosthetic Infection in Patients with Inflammatory Arthritis

BACKGROUND The serum erythrocyte sedimentation rate and C-reactive protein level, as well as the synovial fluid white blood-cell count with differential, are commonly used tests for the diagnosis of periprosthetic joint infection; however, their utility for the diagnosis of periprosthetic joint infection in patients with inflammatory arthritis is unknown. METHODS Eight hundred and three patients undergoing 871 consecutive hip and knee arthroplasties (including sixty-one in patients with inflammatory arthritis and 810 in patients with noninflammatory arthritis) were prospectively evaluated for periprosthetic joint infection. The erythrocyte sedimentation rate, C-reactive protein level, and synovial fluid white blood-cell count with differential were obtained routinely. Receiver operating characteristic curves were used to establish optimal thresholds for the diagnosis of periprosthetic joint infection, and the area under the curve was calculated to determine the overall accuracy of these tests for patients with inflammatory compared with noninflammatory arthritis. RESULTS The utility of all serum and synovial tests for predicting chronic periprosthetic joint infection was similar for patients with noninflammatory and inflammatory arthritis. The optimal cutoffs in patients with noninflammatory and inflammatory arthritis were 32 and 30 mm/hr, respectively, for the erythrocyte sedimentation rate; 15 and 17 mg/L, respectively, for the C-reactive protein level; 3450/μL and 3444/μL, respectively, for the synovial fluid white blood-cell count; and 78% and 75%, respectively, for the differential. The areas under the curves were similar for the two groups (84.9% and 85.0%, respectively, for the erythrocyte sedimentation rate; 88.5% and 85.1%, respectively, for the C-reactive protein level; 94.5% and 93.8%, respectively, for the synovial fluid white blood-cell count, and 95.0% and 93.6%, respectively, for the differential). Finally, the sensitivities, specificities, negative predictive values, and positive predictive values for all tests were also comparable in both groups. The rate of periprosthetic joint infection was significantly higher following procedures in patients with inflammatory arthritis than following procedures in patients with noninflammatory arthritis (31% compared with 18%; p = 0.013). CONCLUSIONS The erythrocyte sedimentation rate, C-reactive protein level, and synovial fluid white blood-cell count with differential are useful for diagnosing periprosthetic joint infection in patients with inflammatory as well as noninflammatory arthritis, with similar optimal cutoff values and overall testing performance. The synovial fluid white blood-cell count and differential performed the best for the diagnosis of periprosthetic joint infection. Physicians evaluating patients with a failed or painful total hip or knee arthroplasty should not assume that elevation of the erythrocyte sedimentation rate, C-reactive protein level, and synovial fluid white blood-cell count with differential is secondary to inflammatory arthropathy; rather, elevation of these markers may indicate periprosthetic joint infection, and further evaluation for infection is warranted.

Dilute Betadine Lavage Before Closure for the Prevention of Acute Postoperative Deep Periprosthetic Joint Infection

This study evaluated the efficacy of a dilute Betadine (Purdue Pharma, Stamford, Conn) lavage in preventing early deep postoperative infection after total hip (THA) and knee (TKA) arthroplasty. A protocol of dilute Betadine lavage (0.35%) for 3 minutes was introduced to the practice of the senior author in June 2008. A total of 1862 consecutive cases (630 THA and 1232 TKA) performed before this were compared with 688 consecutive cases (274 THA and 414 TKA) after for the occurrence of periprosthetic infections within the first 90 days postoperatively. Eighteen early postoperative infections were identified before the use of dilute Betadine lavage, and 1 since (0.97% and 0.15%, respectively; P = .04). There were no significant demographic differences between the 2 groups. Betadine lavage before wound closure may be an inexpensive, effective means of reducing acute postoperative infection after total joint arthroplasty.

Irrigation and Debridement for Periprosthetic Infections : Does the Organism Matter?

Irrigation and debridement (I&D) is an attractive treatment alternative for periprosthetic joint infection (PJI). Irrigation and debridement failure rates average 64% (range, 10.5%-84%) and may be associated with causative organism type and virulence. The study objective was to compare revision rates for PJI caused by streptococcal organisms to other organisms treated with I&D. A multicenter retrospective cohort study of 200 consecutive PJIs treated with I&D was performed. Failure was defined as reoperation for PJI. Failure rate for streptococcal infections was 65% (20/31) compared with 71% (84/119) for other organisms. Failure rate for sensitive Staphylococcus was 72% (48/67) compared with a 76% (22/29) failure rate for resistant Staphylococcus. These results indicate that eradication rates of I&D for a streptococcal PJI are comparable with other causative organisms. Irrigation and debridement should play a limited role in the PJI treatment algorithm regardless of organism type.

Extensor mechanism allograft reconstruction for extensor mechanism failure following total knee arthroplasty.

BACKGROUND Extensor mechanism disruption following total knee arthroplasty is a rare but devastating complication. The purpose of this study was to report our experience with extensor mechanism allograft reconstruction for chronic extensor mechanism failure. METHODS Fifty consecutive extensor mechanism allograft reconstructions were performed in forty-seven patients with a mean age of 67.6 years who were followed for a mean time of 57.6 months (range, twenty-four to 125 months). The operative technique included the use of a fresh-frozen, correctly sized full extensor mechanism allograft that was tensioned tightly in full extension. Patients were evaluated clinically with use of the Knee Society score, and reconstructions were considered failures if the patient had a score of <60 points or a recurrent extensor lag of >30° or if they required revision or removal of the allograft. RESULTS Nineteen reconstructions (38%) were considered failures, including four revised to a second extensor mechanism allograft due to failure of the allograft, five for deep infection, and ten considered clinical failures secondary to a Knee Society score of <60 points or an extensor lag of >30°. The mean Knee Society score improved from 33.9 to 75.9 points (p<0.0001). The estimated Kaplan-Meier survivorship with failure for any reason as the end point was 56.2% (95% confidence interval, 39.4% to 70.1%) at ten years. CONCLUSIONS Extensor mechanism disruption following total knee arthroplasty is a difficult complication to treat, with modest outcomes. Extensor mechanism allograft reconstruction is a reasonable option; however, patients must be informed regarding the substantial risk of complications, and although initial extensor mechanism function may be restored, expectations regarding longer-term outcomes are more guarded.

Operative treatment of early peri-prosthetic femur fractures following primary total hip arthroplasty.

The risk factors for and results of operatively treated peri-prosthetic femoral fractures sustained within 90 days following primary THA were evaluated. 5,313 consecutive THAs were reviewed and 32 (0.60%) fractures were identified which included 9 A(g), 2 B(1), 18 B(2), 1 B(3), and 2 A(g)/B(2) fractures. 19 (61%) patients sustained 23 complications including 9 greater trochanter non-unions, 2 femoral shaft non-unions, 3 patients with Brooker III HO, and 2 deep infections. 7 patients (23%) required a second operative procedure and one patient required a third. Peri-prosthetic fractures were associated with advancing age, female gender, developmental hip dysplasia, and cementless metaphyseal engaging components, particularly flat wedge tapers. Overall, operative treatment of acute peri-prosthetic fractures is associated with a high rate of complications (61%) and re-operation (23%).

Acetabular distraction: An alternative Approach to Pelvic Discontinuity in failed Total Hip Replacement

A pelvic discontinuity occurs when the superior and inferior parts of the hemi-pelvis are no longer connected, which is difficult to manage when associated with a failed total hip replacement. Chronic pelvic discontinuity is found in 0.9% to 2.1% of hip revision cases with risk factors including severe pelvic bone loss, female gender, prior pelvic radiation and rheumatoid arthritis. Common treatment options include: pelvic plating with allograft, cage reconstruction, custom triflange implants, and porous tantalum implants with modular augments. The optimal technique is dependent upon the degree of the discontinuity, the amount of available bone stock and the likelihood of achieving stable healing between the two segments. A method of treating pelvic discontinuity using porous tantalum components with a distraction technique that achieves both initial stability and subsequent long-term biological fixation is described.

The Use of Trabecular Metal Cones in Complex Primary and Revision Total Knee Arthroplasty

Trabecular metal cones are one option for treating osseous defects during TKA. A total of 83 consecutive TKAs utilizing cones with an average of 40 months follow-up were reviewed. There were 24 males and 59 females, with an average age of 69 years old. Four were complex primary and 79 were revision procedures. Of 83 patients, 10 (12%) required repeat revision surgery (8 infections, one periprosthetic fracture, one aseptic loosening) and overall, 37 of 83 patients (45%) experienced at least one complication. Of 73 unrevised knees, 72 (99%) demonstrated radiographic evidence of osseointegration. Despite a high complication rate in this population, trabecular metal cones represent an attractive option for managing bone loss in complex primary and revision TKA with a high rate of osseointegration.

Caspase Inhibition Blocks Cell Death and Results in Cell Cycle Arrest in Cytokine-deprived Hematopoietic Cells

Cytokine deprivation has been classically used to study molecular processes of apoptosis. Following interleukin (IL)-3 withdrawal in FL5.12 cells, Bax undergoes a conformational change that results in its mitochondria targeting, cytochrome c release, activation of caspase-9, and apoptosis. Cells overexpressing Casp9DN (dominant negative caspase-9) or treated with the caspase inhibitor Q-VD-OPh increased viability but failed to increase clonogenic survival. We find that caspase-inhibited cells had a significant fraction of viable cells (herein termed “rescued” cells) that failed to initiate cell division after IL-3 add back. The “rescued” cells had reduced mitochondrial potential, stained for active Bax, and had reduced staining with dihydroethidium, an agent sensitive to superoxide levels. Readdition of IL-3 after deprivation demonstrated that Bax activation was reversed, whereas altered 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolylcarbocyanine iodide and dihydroethidium staining persisted for days. Furthermore, the “rescued” cells were resistant to rotenone, an inhibitor of mitochondrial respiration. The cells were highly sensitive to 2-deoxyglucose, an inhibitor of glycolysis and proposed anti-cancer agent. We conclude that the inhibition of caspase-9 allows cells to retain viability, but cells have prolonged mitochondrial dysfunction and enter a unique nondividing state that shares some properties with malignant cells.

Intra-Operative Periprosthetic Fractures Associated With Press Fit Stems in Revision Total Knee Arthroplasty Incidence, Management, and Outcomes

The purpose of this study is to report the incidence, management, and outcomes of periprosthetic fractures associated with the insertion of press-fit stems during revision total knee arthroplasty (TKA). Immediate and six week post-operative radiographs from 634 stemmed implants (307 femoral, 327 tibial) from 420 consecutive revision TKAs were reviewed. Sixteen tibial (4.9%) and 3 femoral (1%) fractures (combined incidence 3.0%) were identified. All healed uneventfully without operative intervention, with no evidence of implant loosening at a mean of 23 months (range 12 to 47 months). The technique of tightly press fitting stems into the diaphysis is associated with a small rate (3%) of periprosthetic fractures; most were non or minimally displaced, all healed uneventfully with non-operative management and were not associated with implant loosening.