Five year survivorship of primary non-modular stemless constrained knee arthroplasty.

INTRODUCTION: Recent development of stemless non-modular constrained (NMC) condylar components has offered solutions to end of stem pain, canal invasion, and complicated revision. However, supposed improvement in fixation associated with stems has led to some fears about non-modular (NM) devices and aseptic loosening. The purpose of this study was to evaluate the average five-years survivorship and clinical results of this newer primary NM constrained condylar arthroplasty. METHODS: We retrospectively reviewed 184 primary (TKAs) (140 patients) utilizing a newer NMC condylar implant from 1999 to 2008. Pre-operative range of motion and Knee Society function scores were obtained and compared to that of the patients' most recent follow-up. Statistical analysis included Kaplan-Meier survivorship analysis of all knees, with failure defined as the removal of the implant for any reason. RESULTS: Follow-up averaged 5years (range: 2-9). Of the entire cohort, 42 patients are deceased and 14 knees have been revised. Of the 7 patients revised for loosening, 6 were isolated for femoral component loosening (3.3%). There was a significant improvement in both postoperative knee score and function score (p<0.05). The 5-year survival was 97.3%. CONCLUSION: The use of constraint should be judicious and ligament balancing, but we recommend using the least amount of constraint necessary to achieve stability. In addition, because of a significant number of isolated femoral loosenings observed in our cohort of stemless NMC knee prostheses, we recommend the use of a femoral stem with constrained condylar knee prosthesis in patients that have osteopenia and require a constrained knee.

Comprehensive Analysis of a Recalled Modular Total Hip System and Recommendations for Management.

BACKGROUND: Recent total hip arthroplasty designs have introduced modularity at the neck-stem junction. There are reports of failure of this class of designs due to corrosion at the modular junction. The purpose of this study was to evaluate patients implanted with a recently recalled modular total hip arthroplasty system. METHODS: This was a prospective study of 216 total hip arthroplasties in 195 patients performed by a single surgeon. All hips had a titanium-alloy stem, but 199 had a modular cobalt-chromium neck and seventeen were monolithic. The mean patient age was 65.4 years (range, twenty to eighty-eight years); seventy-nine were men and 116 were women. Patients were evaluated for infection and with metal ion assays and MRI (magnetic resonance imaging). Intraoperative tissue samples were graded, and retrieved implants were examined. RESULTS: At a mean follow-up of 19.3 months, eighty (37%) of 216 hips had been revised. An adverse local tissue reaction (ALTR) was the cause for revision in seventy-three of these eighty hips; all had the modular neck design. Assay results for the patients requiring revision showed higher levels of cobalt (mean, 8.6 ng/mL) than chromium (mean, 1.8 ng/mL). MRI showed moderate to severe levels of synovial response in sixty-three of 166 hips. The mean ALVAL (aseptic lymphocyte-dominated vasculitis-associated lesion) score for the revised hips was 8.1. Corrosion was visible on all tapers at the neck-stem junction but not the head-neck junction. CONCLUSIONS: Early failures of modular total hip arthroplasty occur due to fretting and corrosion at the neck-stem junction, resulting in ALTR. Surveillance utilizing metal ion levels and MRI may be indicated for all patients regardless of symptoms, as the early survivorship is poor and the ultimate failure rate may be catastrophically high.

A Novel Assessment of Braking Reaction Time Following THA Using a New Fully Interactive Driving Simulator.

BACKGROUND: After total hip replacement surgery, patients are eager to resume the activities of daily life, particularly driving. Most surgeons recommend waiting 6 weeks after surgery to resume driving; however, there is no evidence to indicate that patients cannot resume driving earlier. QUESTIONS/PURPOSES: Our purpose was to evaluate when in the recovery period following THA that patients regain or improve upon their preoperative braking reaction time, allowing them to safely resume driving. METHODS: We measured and compared pre- and postoperative braking reaction times of 90 patients from 3 different surgeons using a Fully Interactive Driving Simulator (Simulator Systems International, Tulsa, OK). We defined a return to safe braking reaction time as a return to a time value that is either equal to or less than the preoperative braking reaction time. RESULTS: Patients tested at 2 and 3 weeks after surgery had slower braking reaction times than preoperative times by an average of 0.069 and 0.009 s, respectively. At 4 weeks after surgery, however, patients improved their reaction times by 0.035 s (p = 0.0398). In addition, at 2, 3, and 4 weeks postoperatively, the results also demonstrated that patient less than 70 years of age recovered faster. CONCLUSIONS: Based upon the results of this study, most patients should be allowed to return to driving 4 weeks following minimally invasive primary total hip arthroplasty.

Weight changes after total hip or knee arthroplasty: prevalence, predictors, and effects on outcomes.

BACKGROUND: Conflicting evidence exists with regard to weight loss after total hip arthroplasty or total knee arthroplasty. The purposes of this study were to determine whether patients lose weight after total hip arthroplasty or total knee arthroplasty, whether there are predictors of weight change after total hip arthroplasty or total knee arthroplasty, and whether weight changes after total hip arthroplasty or total knee arthroplasty affect patient-reported outcomes. METHODS: Using our institutional registry, we evaluated the two-year change in self-reported body mass indices for all patients who underwent elective, unilateral total hip arthroplasty or total knee arthroplasty for osteoarthritis. A 5% change in body mass index was considered clinically meaningful. Patient-reported outcomes were compared between patients who underwent total hip arthroplasty and those who underwent total knee arthroplasty and between obesity classes, on the basis of whether patients gained, lost, or maintained weight. RESULTS: We reviewed 3893 total hip arthroplasties and 3036 total knee arthroplasties. Of the patients who underwent total joint arthroplasty, 73% (2850 patients) in the total hip arthroplasty group and 69% (2090 patients) in the total knee arthroplasty group demonstrated no change in body mass index. Patients who underwent total knee arthroplasty were more likely to lose weight than patients who underwent total hip arthroplasty. Increasing preoperative obesity correlated with a greater likelihood of weight loss. Patients who underwent total knee arthroplasty and lost weight demonstrated better clinical outcome scores, but weight gain in general was associated with inferior clinical outcomes. Greater body mass index, total knee arthroplasty, and female sex were significant predictors of weight loss (p < 0.05). Better preoperative functional status was significantly associated with a lower likelihood of weight gain (p < 0.05). CONCLUSIONS: Most patients maintained their body mass index after total hip arthroplasty or total knee arthroplasty. Female patients, patients with higher preoperative body mass index, and those who underwent total knee arthroplasty were more likely to lose weight after surgery. LEVEL OF EVIDENCE: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Preoperative predictors of postoperative opioid usage, pain scores, and referral to a pain management service in total knee arthroplasty.

BACKGROUND: Little is known about preoperative predictors of postoperative pain and referral to a recuperative pain management service after total knee arthroplasty (TKA). QUESTIONS/PURPOSES: We sought to identify the preoperative predictors of postoperative pain scores, referral to a pain management service, and narcotic usage in patients undergoing primary total knee arthroplasty. METHODS: We performed a prospective cohort study of 97 TKAs from a single surgeon. Pre and 6-week postoperative WOMAC, visual analog pain scale (VAS) scores, narcotic usage, and catastrophizing pain scores were collected. RESULTS: After adjusting for all other variables, higher age and catastrophizing pain scores were associated with lower odds of postoperative opioid usage. Increasing age and BMI were associated with lower odds of being referred to pain management. There was no relationship between self-reported preoperative pain tolerance and postoperative change in WOMAC or VAS pain scores. CONCLUSIONS: This information may help surgeons advise their patients preoperatively and set expectations during the recovery period.

Design modifications may improve range of motion following posteriorly stabilized total knee replacement: a matched pair study.

BACKGROUND: Our institution's latest knee implant design modifications aimed to decrease anterior knee pain, reduce the amount of bone that is resected in the femoral box, and improve range of motion. QUESTIONS/PURPOSES: Does this new knee design achieve desired clinical improvement in our patient population? This study was designed to compare our new design to that of its predecessor in a matched pair analysis. METHODS: A consecutive group of 100 knees underwent total knee arthroplasty using the newer box reamer (BR) posterior-stabilized design was matched by age, gender, and body mass index (BMI) to patients with the classic posterior-stabilized (PS) component. Average follow-up was 29.6 months (range 21-47) in the new group. Preoperative range of motion (ROM) and clinical scores, such as Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Knee Society Scores, were obtained and compared to the patients' most recent follow-up. Manipulation under anesthesia (MUA) and revision of the implant for any reason were also analyzed. Ability to attain ROM of >120°, >130°, and >140° was also determined in each cohort. RESULTS: At 2-year follow-up, 41% of BR knees achieved >130° flexion compared with 19% in the PS design group. WOMAC improved from pre-op 47 to 80 at 1 year in the newer BR design group and 48 to 80 in the classic PS design group. There were 9 MUAs in the newer BR design group compared with 14 in the classic PS design group. There were three revisions in the PS group and none in the BR group. CONCLUSIONS: Design improvements to this newer knee allowed more patients to achieve greater flexion and appear to have achieved clinical and design goals of the engineering modifications.

Prophylaxis for thromboembolic disease and evaluation for thrombophilia.

Patients treated with total hip or knee arthroplasty are at risk for venous thromboembolic disease. Laboratory evaluation of thrombophilia can help to better identify patients at higher risk for venous thromboembolic disease, and newer methods that test for genetic factors continue to evolve; however, more research is needed to justify routine testing for thrombophilia. Research studies have yielded differing results in determining the most appropriate prophylactic regimen. Both pharmaceutical and mechanical treatments are commonly used for prophylaxis. New pharmacologic prophylaxes include the Xa inhibitor rivaroxaban and the thrombin inhibitor dabigatran etexilate. The newest mechanical device used to prevent venous thromboembolism is a miniature, mobile, battery-operated pneumatic system called Continuous Enhanced Circulation Therapy. The American College of Chest Physicians guidelines and the American Academy of Orthopaedic Surgeons clinical guideline were reviewed to directly compare specific agents and balance the risks of venous thromboembolism. Future studies for venous thromboembolic prophylaxis will continue to evaluate new oral agents, improved pneumatic compression devices, and improved methods to decrease bleeding in the immediate postoperative period.

Are bilateral total joint arthroplasty patients at a higher risk of developing pulmonary embolism following total hip and knee surgery?

Despite developments in prophylactic methods, venous thromboembolism (VTE) continues to be a serious complication following total joint arthroplasty. The new AAOS/ACCP guidelines on preventing pulmonary embolism (PE) after total hip/knee arthroplasty (THA/TKA) do not make specific recommendations for bilateral vs. unilateral procedures. In-patient PE rates were examined for patients undergoing unilateral or simultaneous bilateral TKA/THA at our institution in 2011. Of the 7,437 THA/TKA surgeries completed at our institution in 2011, 36 patients suffered from PE (0.48%). The rate of PE for unilateral TKA was 0.61% vs. 1.87% for bilateral (P < 0.001) and for unilateral THA was 0.17% vs. 0.52% for bilateral THA. Despite patients being screened before being cleared to undergo bilateral THA/TKA, they remain at higher risk for VTE.

Reduction in bone volume resection with a newer posterior stabilized total knee arthroplasty design.

BACKGROUND: Posterior stabilized total knee arthroplasty requires an intercondylar notch to accommodate the cam housing that articulates with the tibial post to create femoral rollback required for deep flexion. The volume of bone resected for the intercondylar notch varies with implant design, and newer designs may accommodate high flexion with less bone resection. QUESTIONS/PURPOSES: This study aims to analyze the bone volume and density resected from the intercondylar notch for three posterior stabilized implants from a single company: a Posterior Stabilized (PS) system, a Hi-Flex system (HF), and a rounded new box-reamer (RB) system and to further assess whether the newer RB with a cylindrical cutting tool would preserve more native bone. MATERIALS AND METHODS: Using a computer model, the PS, HF, and RB femoral components were digitally implanted into CT scans of 19 cadaver femurs. Nine cadavers were fit with a size 4 implant, six with size 3, and four with a size 2. The volume of intercondylar bone resected digitally for femoral preparation was measured. Bone density was measured by CT scans in Hounsfield units (HU). A paired t test was used to compare the mean volume of bone resected for each implant. RESULTS: For the size 4 femurs, the newer RB design removed 8% less intercondylar bone than the PS design (7,832 ± 501 vs. 8,547 ± 377 mm(3), p < 0.001) and 28% less bone than the HF design (7,832 ± 501 vs. 10,897 ± 444 mm(3), p < 0.001). The average HU for size 4 femurs for RB design was 427 ± 72 (PS = 399 ± 69, p < 0.001; HF = 379 ± 66, p < 0.001). For the size 3 femurs, the RB design removed 12% less intercondylar bone than the PS (6,664 ± 786 vs. 7,516 ± 648 mm(3), p < 0.001) and 27% less bone than the HF (6,664 ± 786 vs. 9,078 ± 713 mm(3), p < 0.001). HU for size 3 femurs for the RB design was 452 ± 70 (PS = 422 ± 53, p < 0.1; HF = 410 ± 59, p < 0.01). For the size 2 femurs, the RB design removed 5% less intercondylar bone than the PS (5,730 ± 552 vs. 6,009 ± 472 mm(3), p < 0.01) and 22% less bone than the HF (5,730 ± 552 vs. 7,380 ± 532 mm(3), p < 0.001). HU for size 2 femurs for the RB design was 430 ± 48 (PS = 408 ± 55, p < 0.01; HF = 385 ± 56, p < 0.01). CONCLUSIONS: The newer RB design removes less bone from the intercondylar notch than the classic PS and HF designs in all sizes tested. The bone-conserving cuts incorporated into this newer implant design appear to preserve native bone without compromising design objectives.