Christian P. Christensen

Clinical Performance of Highly Cross-Linked Polyethylenes in Total Hip Arthroplasty

Aseptic loosening secondary to wear-debris-induced osteolysis has been identified as the leading cause of late failure of total hip arthroplasty. Highly cross-linked polyethylene acetabular liners were developed as one approach to reducing this wear. Preclinical laboratory wear testing showed a number of cross-linked polyethylenes to have dramatically less wear than the polyethylene that had been in use for several decades. After the initial bedding-in phase (one to two years), the percent reductions in the wear rate, as indicated by the amount of penetration of the head into the socket evident on serial radiographs, have been comparable with what was predicted from preclinical hip-simulator testing of the highly cross-linked polyethylenes. To our knowledge, there have been no reports of clinically relevant osteolysis that was clearly attributable to wear of a highly cross-linked polyethylene acetabular liner. However, the clinical performance of these materials should be closely monitored with long-term follow-up.

Static and mobile antibiotic-impregnated cement spacers for the management of prosthetic joint infection.

&NA; Two‐stage treatment is currently the most common approach for management of an infected joint prosthesis in the United States. Static antibiotic‐impregnated polymethylmethacrylate cement spacers have traditionally been used; increasingly, however, mobile or articulating spacers are being utilized. Advocates of mobile spacers have cited potential advantages, including more effective maintenance of the joint space, allowing for limited weight bearing and facilitating joint motion; possible reduction in bone loss; and local delivery of antibiotics. Because a variety of materials and construction methods is used to make knee and hip spacers, comparisons are difficult. Randomized, prospective studies are needed to determine the best spacers for total knee and total hip arthroplasties.

Greater prevalence of wound complications requiring reoperation with direct anterior approach total hip arthroplasty.

The purpose of this retrospective study was to compare wound complication rates between primary THAs performed via a posterior or direct anterior approach. From our prospective outcomes registry, we identified 1288 primary THAs performed via a posterior approach and 505 via a direct anterior approach. The direct anterior approach resulted in a significantly greater number of wound complications that required reoperation than the posterior approach (7/505 (1.4%) vs. 3/1,288 (0.2%), P=0.007). As such, patients should be counseled on the potential increased risk of early wound complications with the direct anterior approach, and future research is needed to determine if alternative closure techniques can reduce the risk of wound complication.

Effect of periarticular corticosteroid injections during total knee arthroplasty. A double-blind randomized trial.

BACKGROUND Multimodal pain-control protocols that include periarticular injections have been reported to decrease pain and improve early outcomes following total knee arthroplasty. While injections containing a corticosteroid have been demonstrated to be safe and effective, we are not aware of any randomized trials in which the specific effect of the corticosteroid on early postoperative outcomes has been evaluated. The purpose of this double-blind study was to compare the clinical efficacy of periarticular injections consisting of bupivacaine, morphine, epinephrine, clonidine, and cefuroxime as well as a corticosteroid (methylprednisolone acetate) with the efficacy of periarticular injections consisting of the same agents but without the inclusion of a corticosteroid. METHODS Seventy-six patients were randomized to either the no-steroid group (thirty-seven patients) or the steroid group (thirty-nine patients). Pain and narcotic consumption during the inpatient stay and the length of the hospital stay were recorded. Knee Society scores, the range of motion, and the occurrence of any complications were recorded preoperatively and at six and twelve weeks after the surgery. RESULTS The hospital stay was significantly shorter for patients in the steroid group (2.6 days compared with 3.5 days in the no-steroid group; p = 0.01). No significant group differences in terms of pain, narcotic consumption, outcome scores, or motion were identified. There were three complications in the steroid group: two patients required a manipulation under anesthesia, and the knee joint became infected in another patient, leading to numerous complications and ultimately death. CONCLUSIONS The periarticular injection of a corticosteroid may reduce the length of the hospital stay following total knee arthroplasty, but it does not appear to improve pain relief, motion, or function in the early postoperative period. While we cannot definitively state that the corticosteroid was a causative factor in the development of the infection at the site of the prosthetic joint, we cannot rule it out either, which raises concern regarding the role of corticosteroids in perioperative pain management following total knee arthroplasty.

Comparison of Patient Function during the First Six Weeks after Direct Anterior or Posterior Total Hip Arthroplasty (THA): A Randomized Study

The purpose of this single-surgeon randomized study was to determine if functional recovery during the early postoperative period differs between the direct anterior (DAA) and posterior approaches (PA). An a priori power analysis indicated that 26 patients per group were needed, and 6-week follow-up data were available for 51 THAs to date. Hospitals stays were significantly shorter for the DAA group (1.4 vs. 2.0 days, P=0.01), and the change in Pain Scores was significantly greater for the DAA group (P=0.04). The DAA group also discontinued use of an assistive ambulatory device at an earlier time (33.0 vs. 43.1 days, P=0.03). Despite these differences, no other subjective or objective functional measures differed between the 2 groups at the 6-week follow-up.

Factors Influencing Patient Satisfaction Two to Five Years After Primary Total Knee Arthroplasty

Between 15% and 20% of primary total knee arthroplasty (TKA) patients have been reported to be dissatisfied with the procedure. With 2 to 5 year follow-up of 768/959 (80%) cruciate-retaining TKAs performed by a single surgeon, we evaluated the prevalence of dissatisfied patients and determined which factors were most related to patient satisfaction. Of the 768 TKAs, 80 were dissatisfied with their procedure (10.4%). Postoperative Knee Society Pain Scores and passive knee flexion were most related to a lack of satisfaction. Age, gender, and BMI did not appear to be related to patient satisfaction. By and large, dissatisfied patients in the current study had not experienced improvements in passive flexion, Pain Scores, or Function Scores when compared to their preoperative state.

Patient and Intraoperative Factors Influencing Satisfaction Two to Five Years After Primary Total Knee Arthroplasty

The purpose of this study was to compare patient demographics and factors recorded at the time of surgery between patients that were either satisfied or dissatisfied with their TKA at mid-term follow-up. From our prospective outcomes database, 989 primary TKAs with complete preoperative and intraoperative data were identified. At mean follow-up of 3.5 years, 94/989 TKAs (9.5%) were not satisfied with their TKA. African American patients were 3.0 times more likely to be dissatisfied than Caucasians (95% CI = 1.5-6.0, P = .003). Patients with less severe degenerative changes were 2.1 times more likely to be dissatisfied (95% CI = 1.3-3.2, P = .001).

The natural progression of synovial fluid white blood-cell counts and the percentage of polymorphonuclear cells after primary total knee arthroplasty: a multicenter study.

BACKGROUND Assessments of the synovial fluid white blood-cell (WBC) count and percentage of polymorphonuclear cells (PMNs) have been reported to be useful in the diagnosis of periprosthetic joint infection. The purpose of this multicenter retrospective study was to evaluate the natural progression of the synovial fluid WBC count, PMN percentage, and total neutrophil count in patients who underwent knee aspiration during the first two years after primary total knee arthroplasty and had no evidence of periprosthetic joint infection. METHODS From April 1999 to March 2012, 571 patients who presented within the first two years after primary total knee arthroplasty underwent knee aspiration as part of an evaluation for periprosthetic joint infection. Patients were categorized into four groups on the basis of the number of days between surgery and arthrocentesis. The synovial fluid WBC count, PMN percentage, and total neutrophil count were compared among the four time periods with use of separate one-way analyses of variance and Tamhane post-hoc analyses. RESULTS Four hundred and fifty-two samples not associated with a periprosthetic joint infection were adequate for analysis. The synovial fluid WBC count, PMN percentage, and total neutrophil count all decreased after the first ninety postoperative days. The synovial fluid WBC count showed an earlier return to a level similar to the two-year time point than the PMN percentage did. The mean total neutrophil count decreased from 2533.2 cells/μL during the first forty-five days to 649.0 cells/μL from forty-six to ninety days, 269.5 cells/μL from three months to one year, and 240.8 cells/μL from one to two years. CONCLUSIONS The synovial fluid WBC count and PMN percentage changed at different rates over the first two years after total knee arthroplasty, with the WBC count exhibiting an initially more rapid decrease and the PMN percentage demonstrating a more linear decrease. Hence, the total neutrophil count, which combines these two parameters, may provide a better method to identify patients with a periprosthetic joint infection. Values for the synovial fluid WBC count, PMN percentage, and total neutrophil count were all significantly elevated in the early postoperative period, and the use of standard cutoff values for the diagnosis of periprosthetic joint infection can lead to false-positive results.

Electromyographic Analysis of Hip Abductor Exercises Performed by a Sample of Total Hip Arthroplasty Patients

Weakness of the hip abductors after total hip arthroplasty may result in pain and/or functional limitation. Non-weight-bearing (NWB) exercises are often performed to target the hip abductors; however, muscle activation of NWB exercises has not been compared to weight-bearing (WB) exercises. Our purpose was to evaluate gluteus medius activation during 2 WB and 2 NWB hip abductor strengthening exercises. Fifteen patients at least 6 weeks post unilateral total hip arthroplasty volunteered for the study. Electromyographic amplitude for each exercise was normalized to each patients maximal voluntary isometric contraction. There were no significant differences in gluteus medius electromyographic amplitudes between the 4 exercises (P = .15). Based on our results, NWB exercises provided no clear benefit in terms of gluteus medius activation when compared to potentially more functional WB exercises in the early postoperative period.

Soft Tissue Releases Affect the Femoral Component Rotation Necessary to Create a Balanced Flexion Gap During Total Knee Arthroplasty

The structures that were released to balance the extension gap were recorded during 1500 consecutive TKA procedures, and the amount of femoral component external rotation (ER) necessary to balance the flexion gap was measured with a tensiometer. The amount of ER necessary to balance the flexion gap significantly decreased as more medial structures were released (1 structure=4.7°, 2=4.1°, 3=2.8°, 4 or more=1.1°, P<0.012), whereas significantly greater ER was necessary when three or more lateral structures were released (1 structure=5.3°, 2=5.5°, 3 or more=8.6°, P<0.03). Soft tissue releases affected the amount of femoral component ER necessary to balance the flexion gap, bringing into question the ability of techniques utilizing bony landmarks to properly align the femoral component in rotation.