No Difference in Blood Loss and Risk of Transfusion Between Patients Treated with One or Two Doses of Intravenous Tranexamic Acid After Simultaneous Bilateral TKA.

BACKGROUND: Tranexamic acid (TXA) is often used to prevent excessive blood loss during bilateral TKA. Although it diminishes blood loss, TXA may have a potentially elevated thrombogenic risk with extra, unnecessary doses of TXA in this high-risk population. To date, the most efficacious dosing protocol in this setting has not yet been ascertained. QUESTIONS/PURPOSES: We compared one versus two doses of intravenous TXA in the setting of same-day bilateral TKA in terms of (1) perioperative blood loss that occurred during the hospital stay, (2) transfusion usage during the hospital stay, and (3) major complications occurring within 30 days of surgery. METHODS: Between August 2013 and October 2016, 309 patients underwent simultaneous bilateral TKA performed by one of five attending surgeons. During that time, indications for same-day bilateral TKA included bilateral knee pathology in which each knee was independently indicated for TKA and the patient preferred bilateral simultaneous TKAs versus staged bilateral surgeries. Patients who had cardiac disease or an American Society for Anesthesiologists physical classification score of greater than 2 were not generally indicated for bilateral simultaneous TKAs. After preoperative clearance from the primary physician and/or specialists as necessary, the decision for bilateral TKA was at the judgment of the operating surgeons. Input from anesthesia occurred at the time of the surgery as the procedure was performed in a sequential fashion allowing for the surgery to be restrained to a single limb if anesthesia identified concerns at the completion of the first TKA. The current retrospective, comparative series compared generally sequential groups in terms of TXA usage. Between August 2013 and July 2015, we used two TXA doses. Patients received 1 g of intravenous TXA as a bolus immediately after the last tourniquet release and were given a 1-g intravenous bolus 6 hours after the initial dose. A total of 167 patients were treated with this approach, of whom 96% (161) are fully analyzed here. Between August 2015 and October 2016, our approach changed to a single TXA dose. The dosing regimen change occurred as a group decision for change of practice and occurred mid-year to coincide with the fellowship year cycle. Patients received a 1-g bolus of intravenous TXA immediately after the final tourniquet release. A total of 105 patients were treated with this approach, of whom 89% (93) are fully analyzed here. An additional 37 patients were excluded because they did not receive any TXA because of a medical contraindication such as history of venous thromboembolism, history of thrombotic stroke, cardiac stent in the past 2 years, atrial fibrillation, or long-term anticoagulation therapy. We compared patients who received one versus two doses in terms of blood loss, transfusion usage, and 30-day major complications. The mean age was 65 years for patients receiving one dose and 67 years for patients receiving two doses (p = 0.17). The one-dose group comprised 67% (62 of 93) women and the two-dose group comprised 61% (98 of 161) women (p = 0.36). Blood loss was defined as change in the hemoglobin level (the last recorded value before discharge subtracted from the preoperative value). During the study period, the decision to transfuse was based on a hemoglobin level less than 8.0 g/dL or at higher levels for symptomatic patients, patients with cardiac disease, or at the discretion of the attending surgeon. We defined complications as major medical events that included cerebrovascular accidents, myocardial infarction, deep vein thrombosis, and pulmonary embolism. RESULTS: With the numbers available, there was no difference in blood loss between patients treated with one and those treated with two doses of TXA (mean hemoglobin decrease -3.5 ± 1.2 g/dL versus -3.5 ± 1.0 g/dL, respectively; mean difference 0.03 g/dL [95% CI -0.2 to 0.3 g/dL]; p = 0.80). No patient in either group received a transfusion. There was no difference in the proportion of patients in either group who experienced a cerebrovascular accident (0% [0 of 93] versus 1% [1 of 161]; p > 0.99), deep vein thrombosis (1% [1 of 93] versus 0% [0 of 161]; p = 0.37), or pulmonary embolism (1% [1 of 93] versus 1% [1 of 161]; p > 0.99). No patient in either the one-dose or two-dose TXA groups experienced a myocardial infarction. CONCLUSION: The findings of this study suggest that a single dose of intravenous TXA may be adequate to control excessive blood loss and reduce blood transfusion in simultaneous bilateral TKA. Despite its short half-life, TXA still appears to be effective in this demanding procedure without requiring prolonged plasma concentrations obtained from multiple doses. Additional high-quality studies are still needed to determine the most appropriate dosing regimen. LEVEL OF EVIDENCE: Level III, therapeutic study.

Lower Extremity Total Joint Arthroplasty Has Minimal Effect on Golf Handicap.

Although the vast majority of arthroplasty surgeons allow patients to return to participation in golf following total knee arthroplasty (TKA) and total hip arthroplasty (THA), there is relatively little published data regarding how TKA or THA affects a patient's golfing ability. The purpose of this study was to determine how golfers' handicaps change following TKA and THA. We mailed a questionnaire to patients who had underwent primary TKA or THA at our institution and asked whether they played golf and for their golf handicap information network (GHIN) number. We then obtained handicap data for each patient that provided a GHIN number. Handicap increased 0.9 strokes 1 year following THA; however, this difference was not statistically significant (p = 0.20). Handicap increased 0.3 strokes 1 year following TKA; however, this difference was not statistically significant (p = 0.29). Our study demonstrates that despite improved implants, surgical techniques, and rehabilitation protocols that golf handicap does not change significantly following lower extremity total joint arthroplasty (TJA). (Journal of Surgical Orthopaedic Advances 29(4):216-218, 2020).

Use of intraoperative X-rays to optimize component position and leg length during total hip arthroplasty.

Proper femoral and acetabular component position and leg length equality are important intraoperative considerations during total hip arthroplasty. Unfortunately, traditional surgical techniques often lead to suboptimal component position, and such deviations have been associated with increased rates of prosthetic wear, dislocation, component loosening, and patient dissatisfaction. Although surgical navigation has been shown to improve reproducibility of component alignment, such technology is not universally available and is associated with significant costs and additional surgical/anesthetic time. In the current study, we found that a routine intraoperative pelvic radiograph could successfully identify malpositioned components and leg length inequalities and could allow for successful correction of identified problems. Unexpected component malposition and leg length inequality occurred in only 1.5% of cases where an intraoperative pelvic radiograph was utilized.

Poor short term outcome with a metal-on-metal total hip arthroplasty.

Metal-on-metal (MoM) bearings for total hip arthroplasty (THA) have come under scrutiny with reports of high failure rates. Clinical outcome studies with several commercially available MoM THA bearings remain unreported. We evaluated 78 consecutive MoM THAs from a single manufacturer in 68 patients. Sixty-six received cobalt-chrome (CoCr) monoblock and 12 received modular titanium acetabular cups with internal CoCr liners. Femoral components were titanium with modular necks. At average 2.1 years postoperatively, 12 THAs (15.4%) demonstrated aseptic failure (10 revisions, 2 revision recommended). All revised hips demonstrated capsular necrosis with positive histology reaction for aseptic lymphocytic vasculitis-associated lesions/adverse local tissue reactions. Prosthetic instability following revision surgery was relatively common. Female gender was a strong risk factor for failure, though smaller cups were not. Both monoblock and modular components fared poorly. Corrosion was frequently observed around the proximal and distal end of the modular femoral necks.

Wear of polyethylene against oxidized zirconium femoral components effect of aggressive kinematic conditions and malalignment in total knee arthroplasty.

Metallic femoral components with ceramic articulating surfaces can substantially lower polyethylene (PE) wear during walking activities under conditions of normal knee alignment. It is unknown whether these types of components can maintain low wear rates under conditions of knee malalignment and the harsher kinematics associated with younger, athletically active patients. Wear was measured in non-cross-linked, ethylene oxide-sterilized PE inserts against oxidized zirconium or cobalt-chrome femoral components in a knee wear simulator. The vertical load was modified to replicate knee varus malalignment of 3°, and the range of tibial rotation was increased to 20°. Mean gravimetric and volumetric wear rate over 5 million cycles was 55% lower in the oxidized zirconium group. An oxidized zirconium femoral component can significantly reduce PE wear under simulated conditions of athletically active patients with modestly malaligned total knee arthroplasty prostheses.

The impact of failed novel technology and technical errors on the revision burden in total hip arthroplasty: what percentage of revision hip arthroplasty was potentially avoidable?

BACKGROUND: Despite the high success rate of total hip arthroplasty (THA), new implant technologies continue to be developed. Although potentially useful, such novel developments may result in unintended consequences, leading to revision surgery, often prematurely. In several instances, new technology that appeared promising was later found to be inferior to existing technology and resulting in early revision surgery. Additionally, technical surgical errors may also lead to early revisions. Some have argued that revisions related to such phenomena are potentially avoidable. The present analysis investigates to what extent the contribution of "failed new technology" and "technical errors" contributes to the revision burden and to the need for premature revision arthroplasty. METHODS: We retrospectively analysed 432 revision THAs and categorised them as either "late revisions" based on survivorship of 10 years or "premature revisions". Among both cohorts, we determined what percentage of revisions were potentially avoidable and due to failed novel technologies and technical errors, and what percent were "unavoidable". RESULTS: Of the 432 revisions, 267 (62%) were considered premature and 38% were considered late. Of the premature revisions, 108 were considered potentially avoidable (81 failed novel technologies, 27 technical errors). CONCLUSIONS: Our data demonstrates that new technology and surgical techniques can result in premature failure of THA. Surgeons should take caution when incorporating new implant technology or surgical techniques into their practice.

Hip and Knee Arthroplasty Outcomes for Nonagenarian Patients.

INTRODUCTION: Studies have previously reported higher complication rates in elective total joint arthroplasty (TJA) for nonagenarians compared with younger cohorts. The purpose of this study was to assess whether nonagenarians were still at increased risk of complications and hospital readmissions by answering three questions: (1) Do nonagenarians have an increased risk of medical complications after TJA compared with octogenarians and septuagenarians? (2) Do nonagenarians have an increased risk of surgical complications after TJA compared with octogenarians and septuagenarians? (3) Do nonagenarians have an increased risk of hospital readmission after TJA compared with octogenarians and septuagenarians? METHODS: A total of 174 patients undergoing primary TJA between 2010 and 2017 were included; 58 nonagenarians (older than 90 years) were matched with 58 octogenarians (age 80 to 84 years) and 58 septuagenarians (age 70 to 74). Groups were matched by sex, diagnosis, surgeon, surgical joint, and year of surgery. Within each group, 31 patients (53%) underwent total hip arthroplasty and 27 patients (47%) underwent total knee arthroplasty. Comorbidities, American Society of Anesthesiologists physical status scores, and Charlson Comorbidity Index scores were captured preoperatively. Complications and readmissions occurring within 90 days postoperatively were evaluated. RESULTS: Nonagenarians had the highest rate of medical complications (33%) compared with octogenarians (14%) and septuagenarians (3%) (P < 0.001). Rates of surgical complications were not statistically different among nonagenarians (12%), octogenarians (9%), and septuagenarians (10%) (P = 0.830). Rates of hospital readmission were highest in nonagenarian patients (11%), but not statistically different compared with octogenarians (5%) or septuagenarians (2%) (P = 0.118). CONCLUSION: Nonagenarians were 3.1 times more likely to have a complication after TJA. The incidence of medical complications was highest in nonagenarians compared with octogenarians and septuagenarians, but rates of orthopaedic complications were similar. Nonagenarians who elect to proceed with TJA should be informed that they have an increased risk of postoperative medical complications compared with younger patients undergoing the same operation. LEVEL OF EVIDENCE: Level III, Therapeutic Study.

Isolated tibial polyethylene insert exchange outcomes after total knee arthroplasty.

UNLABELLED: Total knee arthroplasty (TKA) using a modular design allows isolated tibial polyethylene insert exchange (ITPIE) as a treatment option for isolated polyethylene failure. We asked whether ITPIE in selected patients would provide high survivorship and identified factors predicting success or failure. We retrospectively reviewed 42 patients (42 knees) who underwent ITPIE for instability, stiffness, or aseptic effusions after TKA. All patients had well-aligned and well-fixed components documented by radiographs and intraoperative evaluation. We determined whether patients had been revised and evaluated unrevised patients using the Knee Society rating system. The minimum followup was 2 years (average, 5.6 years; range, 2-11 years). Twelve patients (29%) underwent subsequent revision of their ITPIE (58% survivorship at 11 years). Average time to revision was 3 years. Although mean Knee Society scores improved, nine of the 30 unrevised patients (30%) had persistent pain at followup. Time from index TKA to ITPIE was associated with outcome; ITPIE less than 3 years from index TKA was 3.8 times more likely to undergo rerevision than ITPIE more than 3 years from index TKA. ITPIE for failed TKA is associated with unpredictable outcomes. ITPIE, even with well-defined and narrow indications, should be undertaken with caution. The longer the initial components performed successfully before ITPIE, the greater the likelihood of success after ITPIE. LEVEL OF EVIDENCE: Level II, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Incidence of 'squeaking' after ceramic-on-ceramic total hip arthroplasty.

UNLABELLED: The incidence of hip "squeak" associated with ceramic-on-ceramic bearings has been variably reported, ranging from 0.7% to 20.9%. We determined the patients' perception of squeaking in 306 patients (336 hips) in whom ceramic-on-ceramic total hip arthroplasties (THAs) were performed between 1997 and 2005. A questionnaire regarding hip noise was obtained by telephone. With a minimum followup of 2 years (mean, 3.9 years; range, 2-10 years), 290 patients (320 or 95% of the THAs) completed the questionnaire. Patients reported hip noise in 55 of the 320 THAs (17%); noise was perceived as squeak in 32 of the 320 (10%). Most squeaking hips (29 of 32) were pain-free and symptom-free. One patient was unhappy with his squeaking hip without pain. Our data suggest a much higher incidence of squeak as perceived by patients than previously reported. LEVEL OF EVIDENCE: Level II, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Relaxed Hip Precautions Do Not Increase Early Dislocation Rate Following Total Hip Arthroplasty.

INTRODUCTION: Historically, hip precautions have been prescribed after total hip arthroplasty (THA) to limit certain motions felt to place the arthroplasty construct in a position at increased risk for dislocation. This study aimed to determine whether relaxed hip precautions after primary THA done via a posterolateral approach resulted in a higher early dislocation rate compared with standard hip precautions. METHODS: The hip precaution protocol was changed from standard to relaxed at our institution for all patients with THA in December 2016. One cohort had THA in the 18 months before the protocol change and had standard hip precautions, and the second cohort had THA in the 18 months after the protocol change and had relaxed precautions. We determined the early dislocation rate (within 3 months postoperatively) for both cohorts and controlled for selected demographic and surgical details. RESULTS: The standard precaution group included 597 primary THAs and the relaxed precaution group included 692 hips. No notable differences were found between the groups in terms of age at surgery, body mass index, sex, laterality, or diagnosis. Early dislocation occurred in seven hips (1.2%) in the standard precaution cohort and in nine hips (1.4%) in the relaxed precaution cohort. This difference was not statistically significant (P = 0.77). DISCUSSION: The results of our study suggest that well-trained, high-volume surgeons may potentially relax hip precautions prescribed to the patients after primary THA done via a posterolateral approach without subjecting patients to a markedly higher incidence of dislocation. However, unlike previous studies, this study controlled for femoral head size, which is a well-known confounder for dislocation risk.

Modular femoral head and liner exchange for the unstable total hip arthroplasty.

Outcomes of femoral head and nonconstrained liner exchange in treating hip instability were evaluated. Forty-eight modular component exchanges performed in 45 patients for recurrent hip dislocations were retrospectively reviewed. Mean follow-up was 4.7 years. Overall success rate was 73% (35/48 hips). Thirty-two (67%) of 48 hips experienced no further dislocations. Three patients had 1 dislocation each with no subsequent dislocations. Ten patients (13 hips) had additional surgery to stabilize their hips (27% failure rate). Demographic, clinical, and implant variables were not associated with outcome. Isolated modular component exchange can be successful in treating recurrent hip dislocations; however, a significant failure rate, not easily predicted, exists. This represents the largest series of modular head and nonconstrained liner exchange for hip dislocation (122/125).

Portable compression device and low-molecular-weight heparin compared with low-molecular-weight heparin for thromboprophylaxis after total joint arthroplasty.

This preliminary prospective study to determine the rate of deep venous thrombosis (DVT) examined 277 patients undergoing total knee or total hip arthroplasty (TKA or THA) who were randomized to use a portable, continuous enhanced circulation therapy (CECT) compression device and low-molecular-weight heparin (LMWH) or to receive LMWH alone. Patients were screened for DVT using duplex ultrasound at hospital discharge and followed clinically for 3 months. In TKA, 5 DVTs (6.6%) occurred in the CECT + LMWH group compared with one pulmonary embolism and 14 DVTs (19.5%) in the LMWH group (P = .018). In THA, 1 DVT (1.5%) occurred in the CECT + LMWH group and 2 DVTs (3.4%) occurred in the LMWH group. This preliminary study demonstrated significant reduction in rate of DVT after TKA when the CECT device was combined with LMWH.

A nonsurgical protocol for management of postarthroplasty wound drainage.

Persistent wound drainage after total joint arthroplasty can potentiate periprosthetic joint infection. Although current recommendations are to treat persistent wound drainage with surgical debridement, we believe nonoperative treatment may be successful in selected patients. We performed a retrospective analysis of 25 persistently draining hip and knee arthroplasty wounds treated with a protocol consisting of a combination of surgical site aspiration, closure of open wound edges, cessation of anticoagulants, activity modification, and antibiotics (in select patients). Wound drainage ceased in 24 of 25 wounds treated with this protocol. One patient who continued to drain for 3 more days was successfully treated with surgical debridement and evacuation of hematoma. No patient developed infection. We believe this protocol can be successful in many arthroplasty patients.

Can normal knee kinematics be restored with unicompartmental knee replacement?

BACKGROUND: Unicompartmental replacement can be an alternative to tibial osteotomy in younger, active patients with unicompartmental knee disease. In unicompartmental replacement, the other compartments and knee ligaments are largely untouched. Therefore, it was hypothesized that the knee kinematics after unicompartmental replacement may also be unchanged. To test this hypothesis, knee kinematics and quadriceps tension were recorded before and after replacement with a unicompartmental design and then with a tricompartmental design. METHODS: Six human cadaver knees were tested before implantation, after implantation with a bicruciate-retaining unicompartmental knee prosthesis, and after implantation with a posterior cruciate-retaining tricompartmental knee prosthesis. The unicompartmental prosthesis was initially implanted, and it was then revised to a total condylar knee replacement. The knee kinematics were measured with use of an electromagnetic tracking device while the knee was put through dynamic simulated stair-climbing under peak flexion moments of approximately 40 N-m. Quadriceps tension was also measured for all three conditions. RESULTS: No significant differences in tibial axial rotation were noted between the intact and unicompartmental conditions. However, tricompartmental replacement significantly affected tibial axial rotation (p = 0.001). Femoral rollback was not significantly affected by either unicompartmental or tricompartmental arthroplasty. Quadriceps tension was also similar among all three conditions. CONCLUSIONS: In this in vitro cadaver study, the tricompartmental replacement significantly changed knee kinematics while the unicompartmental replacement preserved normal knee kinematics.

A minimum 5-year follow-up of an oxidized zirconium femoral prosthesis used for total knee arthroplasty.

BACKGROUND: Bearing surface wear remains a potential concern amongst younger patients undergoing total knee arthroplasty (TKA). Because of the potential for lower prosthetic wear rates, oxidized zirconium is a potentially attractive bearing surface for TKA in young, active patients. This material is also well suited for patients with suspected nickel sensitivities as it has no measurable nickel content, in contrast to standard femoral bearings made of cobalt-chromium alloys. Although in vitro testing on knee wear simulators has demonstrated favorable wear characteristics of oxidized zirconium compared to traditional cobalt-chrome bearings, in vivo clinical outcome data with this novel bearing surface are sparse. METHODS: We retrospectively reviewed 109 consecutive TKAs in 82 patients at a minimum of five years postoperatively to determine prosthetic survivorship and to assess whether any adverse clinical consequences could be attributed to this bearing. Knees were evaluated with Knee Society scores, UCLA activity scores, clinical examinations, and radiographs. The mean age for this cohort was 58.7 years. RESULTS: Survivorship free of bearing related complications was 100% at a minimum of five years post-surgery. There were no revisions for loosening, osteolysis, implant failure, or deep infection. There were no knees with radiographic failure, visible wear, loosening, or osteolysis. CONCLUSION: Oxidized zirconium remains an attractive option for patients with nickel sensitivities and in those patients at risk for prosthetic wear due to young age or high activity levels.

Reversal of acute ischemic stroke after THA using tissue plasminogen activator.

Acute ischemic stroke is a potentially catastrophic medical emergency. Recently, successful reversal of the neurologic deficits associated with major ischemic strokes has been accomplished in selected patients through the use of intravenous tissue plasminogen activator (tPA), an agent that can accomplish thrombolysis of arterial clots if given within the first few hours after the onset of stroke. Because tPA works by thrombolysis of fresh clots, a potential exists for catastrophic hemorrhage if given to acute postoperative patients. Therefore, the use of tPA has never been studied in postoperative patients, and the safety of the drug in postoperative patients is unknown.The author describes a patient who had an acute ischemic stroke 2 days after total hip arthroplasty who was successfully treated with tPA without major complications. The patient was 51 years old and developed progressive facial droop, right arm paralysis, and dysarthria 2 days after elective hip arthroplasty. Imaging confirmed occlusion of the left middle cerebral artery. Neurologic recovery was believed to be unlikely without tPA. After tPA administration, the patient had full neurologic recovery within minutes but did develop a large (nondraining) hematoma and severe ecchymosis at the surgical site; a drop in hematocrit required 3 units of packed red blood cell transfusion. The wound did not develop skin necrosis, infection, or compartment syndrome, and the hematoma resolved within several weeks without the need for surgical intervention.The author describes the patient's specific circumstances, the decision-making process behind the use of tPA, and the need for contingency plans in the event that severe uncontrolled hemorrhage occurs. This information may be useful if other surgeons are faced with the dilemma of a major stroke in acute postoperative patients.

A comparison of standard and high-flexion knees: are we getting what we expected?

Some patients have been less than satisfied with flexion after total knee arthroplasty (TKA). As early designs provided limited flexion, companies have developed high-flexion designs. We conducted a study to compare flexion between 2 standard and 3 high-flexion designs and to compare clinical and radiographic postoperative flexion. Clinical and radiographic measurements were obtained by 3 independent orthopedists. Clinical flexion, with the patient maximally bending his or her knee as far as possible, was measured with a goniometer, recorded, and compared with measurements from lateral radiographs of the knee in the same position. A total of 144 knees (108 patients) were included in the study. Mean preoperative flexion was 110° for both groups, and mean postoperative flexion was 111° clinically and 109° radiographically for the standard designs, and 114° clinically and 117° radiographically for the high-flexion designs (P<.05). The groups had similar preoperative and postoperative Knee Society knee and function scores. Measurements obtained by the 3 independent examiners were highly correlated. Compared with the standard designs, the highflexion designs demonstrated statistically significantly more flexion, though the clinical increase in flexion was relatively small (3º).

Measured flexion following total knee arthroplasty.

Postoperative flexion is an important factor in the outcome of total knee arthroplasty. Although normal activities of daily living require a minimum of 105° to 110° of flexion, patients from non-Western cultures often engage in activities such as kneeling and squatting that require higher flexion. The desire to achieve greater flexion serves as the driving force for prosthetic modifications, including high-flexion designs. Techniques used to measure knee flexion and knee position during measurement are not often described or are different depending on the examiner. The purpose of this study was to compare active (self) and passive (assisted) flexion after successful total knee arthroplasty for 5 prostheses (2 standard and 3 high-flexion) using clinical (goniometer) and radiographic (true lateral radiograph) measurement techniques by different independent examiners.At a mean follow-up of 2.7 years (range, 1-5.6 years), a total of 108 patients (144 total knee arthroplasties) had completed the study. Mean postoperative active flexion was 111° clinically and 109° radiographically for the standard designs and 114° clinically and 117° radiographically for the high-flexion designs. Adding passive flexion increased flexion to 115° clinically and 117° radiographically for the standard designs and 119° clinically and 124° radiographically for the high-flexion designs. Flexion differences between the 2 measurement techniques (active vs passive and clinically vs radiographically) were statistically significant (P<.05). These findings demonstrate the importance of describing how flexion is measured in studies and understanding how the method of measurement can affect the findings.

Effect of tibial component varus on wear in total knee arthroplasty.

INTRODUCTION: Malalignment can result in poor clinical outcomes and increased wear. However, component malalignment can occur even when overall limb mechanical axis is within the normal anatomic range. We studied the effect of component malalignment in the presence of acceptable knee alignment in knee arthroplasty. METHODS: Sixteen tibial inserts retrieved at revision surgery were laser-mapped to measure wear. Average implantation duration was 7.7 years (range, 1 to 13). Early (postprimary) and final (prerevision) radiographs were analyzed for overall alignment (limb, femoral and tibial components) and osteolysis. RESULTS: The tibial components were initially aligned in a mean of 1.3 ± 1.7° varus (range, -1.5 to 4.5°), which increased to 3.2 ± 2.9° (range, -2.0 to 8.0°) at the time of revision (p=0.05). Tibial components initially placed in greater than 3° varus were associated with almost twice the volumetric penetration rate. Anatomic knee angles were 5.4 ± 0.9° valgus (range, 4.0 to 7.0°) in the post-primary radiographs and decreased in prerevision radiographs to 3.8 ± 2.6° (range, -1.0 to 7.5°), (p=0.04). DISCUSSION: Tibial varus was associated with increased medial compartment wear and total wear, thus affecting osteolysis in addition to local destruction of the bearing surface. Varus malalignment as low as 3° may result in accelerated wear, even if overall limb alignment is nearly ideal. These results indicate that tibial component alignment is an important factor associated with tibial tray subsidence and polyethylene wear even when limb alignment is neutral.

Two Year Follow-up of the Preservation Unicompartmental Knee Implant.

Reported results of unicondylar knee arthroplasty (UKA) have mixed reviews in comparison with results of tri-compartmental knee arthroplasty (TKA). We prospectively evaluated the short-term results (2 years) of a newer design of a UKA implant (Preservation UKA) with a cobalt-chromium femoral component and an all polyethylene tibial component. Seventy-two patients with intact ligaments and loss of only medial articular cartilage received the Preservation prosthesis. Data were obtained using WOMAC, Knee Society score (KSS), and standard radiographs. WOMAC scores improved by 24 points and KSS improved by 33 points at 2-year follow-up. Mean flexion increased by 4° to126° at 2 years. On X-ray, only one patient had a radiolucency. No fractures occurred. Two knees were revised due to clinical symptoms of medial compartment pain. This 2-year follow-up study of the Preservation UKA shows promising early results. Long-term data would be necessary to compare results with TKA or other unicompartmental replacements.