Results of the Oxford Phase 3 mobile bearing medial unicompartmental knee arthroplasty from an independent center: 467 knees at a mean 6-year follow-up: analysis of predictors of failure.

A retrospective review of 467 Oxford UKAs was performed in 387 patients. Thirty-eight knees (8.1%) were revised to TKA at a mean of 49 months, most commonly for lateral compartment OA (47%). The 5-year cumulative survival using revision to TKA was 98.5%. Revisions required short stems in 26% and augments in 21% of cases. The mobile bearing dislocation rate was 0.64%. Correction of ≥3-5° from the preoperative alignment in a valgus direction was predictive of revision to TKA (P<.0001). Multivariate analysis revealed female gender (P=.002) also was associated with an increased risk of revision. Careful attention to the degree of mechanical axis correction with an overall maintained varus alignment may reduce revision rates for mobile bearing UKA.

Computer-assisted total knee arthroplasty is currently of no proven clinical benefit: a systematic review.

BACKGROUND: Navigated total knee arthroplasty (TKA) may improve coronal alignment outliers; however, it is unclear whether navigated TKA improves the long-term clinical results of TKA. QUESTIONS/PURPOSES: Does the literature contain evidence of better long-term function and lower revision rates with navigated TKA compared with conventional TKA? METHODS: A systematic literature review was conducted of navigated TKA reviewing articles related to coronal alignment, clinical knee and function scores, cost, patient satisfaction, component rotation, anteroposterior and mediolateral stability, complications, and longer-term reports. RESULTS: Coronal plane alignment is improved with navigated TKA with fewer radiographic outliers. We found limited evidence of improvements in any other variable, and function was not improved. The duration of surgery is increased and there are unique complications related to navigated TKA. The long-term benefits of additional increase in accuracy of alignment are not supported by any current evidence. CONCLUSIONS: The findings in reports of navigated TKA should be interpreted with caution. There are few short- and medium- and no long-term studies demonstrating improved clinical outcomes using navigated TKA. Despite substantial research, contradictory findings coupled with reservations about the cost and efficacy of the technology have contributed to the failure of computer navigation to become the accepted standard in TKA. Longer-term studies demonstrating improved function, lower revision rates, and acceptable costs are required before navigated TKA may be widely adopted. In the future, with improvements in study design, methodology, imaging, navigation technology, newer functional outcome tools, and longer-term followup studies, we suspect that navigated TKA may demonstrate yet unrecognized benefits.

Prophylactic antibiotics do not affect cultures in the treatment of an infected TKA: a prospective trial.

UNLABELLED: Prophylactic antibiotics are frequently withheld until cultures are obtained in revision total knee arthroplasty (TKA). We undertook a prospective study to determine whether prophylactic preoperative intravenous antibiotics would affect the results of cultures obtained intraoperatively. We enrolled 25 patients with 26 infected TKAs, a known preoperative infecting organism, and no recent antibiotic therapy. Reaspiration of the infected TKA was performed after anesthesia and sterile preparation. Intravenous antibiotic prophylaxis was then administered and the tourniquet inflated. Intraoperative culture swabs and tissue were obtained at arthrotomy. The timing of events was recorded. Pre- and postantibiotic culture data were analyzed to determine the effect of intravenous preoperative prophylactic antibiotics on cultures obtained intraoperatively. Infections were acute postoperative (four), chronic (19), and acute hematogenous (three). The most common infecting organism was cloxacillin-sensitive Staphylococcus aureus (nine knees [35%]). Preoperative prophylactic antibiotics did not affect the results of intraoperative cultures and we therefore believe should not be withheld before surgery for an infected TKA when an organism has been identified on aspiration preoperatively, and there has been no recent (4 weeks) antimicrobial therapy. LEVEL OF EVIDENCE: Level II, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Minimal incision surgery as a risk factor for early failure of total knee arthroplasty.

A consecutive series of revision total knee arthroplasty (TKA) performed at 3 centers by 5 surgeons for a 3-year period was reviewed. Revisions performed for infection and rerevisions were excluded. Review of clinical and radiographic data determined incision type, sex, age, time to revision, and primary diagnosis at time of revision. Two-hundred thirty-seven first-time revision TKAs were performed, of which 44 (18.6%) had been a minimal incision surgery (MIS) primary TKA and 193 (81.4%) had been a standard primary TKA. Patients with MIS were younger (62.1 vs 66.2 years, P = .02). Most striking was the difference in time to revision, which was significantly shorter for the MIS group (14.8 vs 80 months, P < .001). Minimal incision surgery TKA accounted for a substantial percentage of revision TKA in recent years at these centers. The high prevalence of MIS failures occurring within 24 months is disturbing and warrants further investigation.

Diagnosis of infected total knee: findings of a multicenter database.

UNLABELLED: Although total knee arthroplasty (TKA) is an effective and successful procedure, the outcome is occasionally compromised by complications including periprosthetic joint infection (PJI). Accurate and early diagnosis is the first step in effectively managing patients with PJI. At the present time, diagnosis remains dependent on clinical judgment and reliance on standard clinical tests including serologic tests, analysis of aspirated joint fluid, and interpretation of intraoperative tissue and fluid test results. Although reports regarding sensitivity and specificity of all diagnostic tests in the literature are abundant, the interpretation of the available data has been hampered by the low sample size of these studies. In view of the scope of this important problem and the limitations of previous reports, a large database was assembled of all revision TKA performed at three academic referral centers in order to determine the current status of diagnosis of the infected TKA utilizing commonly available tests. Intraoperative cultures should not be used as a gold standard for PJI owing to high percentages of false-negative and false-positive cases. When combined with clinical judgment, total white cell count and percentage of neutrophils in the synovial fluid more accurately reflects PJI and when combined with hematologic exams safely excludes or confirms infection. LEVEL OF EVIDENCE: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Optimal initial dose adjustment of warfarin in orthopedic patients.

BACKGROUND: Warfarin sodium is commonly prescribed for the prophylaxis and treatment of venous thromboembolism. Dosing algorithms have not been widely adopted because they require a fixed initial warfarin dose (eg, 5 mg) and are not tailored to other factors that may affect the international normalized ratio (INR). OBJECTIVE: To develop an algorithm that could predict a therapeutic warfarin dose based on drug interactions, INR response after the initial warfarin doses, and other clinical factors. METHODS: We used stepwise regression to quantify the relationship between these factors in patients beginning prophylactic warfarin therapy immediately prior to joint replacement. In the derivation cohort (n = 271), we separately modeled the therapeutic dose after 2 and 3 initial doses. We prospectively validated these 2 models in an independent cohort (n = 105). RESULTS: About half of the therapeutic dose variability was predictable after 3 days of therapy: R2 was 53% in the derivation cohort and 42% in the validation cohort. INR response after 3 warfarin doses (INR3) inversely correlated with therapeutic dose (p < 0.001). Intraoperative blood loss transiently, but significantly, elevated the postoperative INR values. Other significant (p < 0.03) predictors were the first and second warfarin doses (+7% and +6%, respectively, per 1 mg), and statin use (-15.0%). The model derived after 2 warfarin doses explained 32% of the variability in therapeutic dose. CONCLUSIONS: We developed and validated algorithms that estimate therapeutic warfarin doses based on clinical factors and INR response available after 2-3 days of warfarin therapy. The algorithms are implemented online at www.WarfarinDosing.org.

Clinical presentation of patients with tears of the acetabular labrum.

BACKGROUND: The clinical presentation of a labral tear of the acetabulum may be variable, and the diagnosis is often delayed. We sought to define the clinical characteristics associated with symptomatic acetabular labral tears by reviewing a group of patients who had an arthroscopically confirmed diagnosis. METHODS: We retrospectively reviewed the records for sixty-six consecutive patients (sixty-six hips) who had a documented labral tear that had been confirmed with hip arthroscopy. We had prospectively recorded demographic factors, symptoms, physical examination findings, previous treatments, functional limitations, the manner of onset, the duration of symptoms until the diagnosis of the labral tear, other diagnoses offered by health-care providers, and other surgical procedures that these patients had undergone. Radiographic abnormalities and magnetic resonance arthrography findings were also recorded. RESULTS: The study group included forty-seven female patients (71%) and nineteen male patients (29%) with a mean age of thirty-eight years. The initial presentation was insidious in forty patients, was associated with a low-energy acute injury in twenty, and was associated with major trauma in six. Moderate to severe pain was reported by fifty-seven patients (86%), with groin pain predominating (sixty-one patients; 92%). Sixty patients (91%) had activity-related pain (p < 0.0001), and forty-seven patients (71%) had night pain (p = 0.0006). On examination, twenty-six patients (39%) had a limp, twenty-five (38%) had a positive Trendelenburg sign, and sixty-three (95%) had a positive impingement sign. The mean time from the onset of symptoms to the diagnosis of a labral tear was twenty-one months. A mean of 3.3 health-care providers had been seen by the patients prior to the definitive diagnosis. Surgery on another anatomic site had been recommended for eleven patients (17%), and four had undergone an unsuccessful operative procedure prior to the diagnosis of the labral tear. At an average of 16.4 months after hip arthroscopy, fifty-nine patients (89%) reported clinical improvement in comparison with the preoperative status. CONCLUSIONS: The clinical presentation of a patient who has a labral tear may vary, and the correct diagnosis may not be considered initially. In young, active patients with a predominant complaint of groin pain with or without a history of trauma, the diagnosis of a labral tear should be suspected and investigated as radiographs and the history may be nonspecific for this diagnosis. LEVEL OF EVIDENCE: Diagnostic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Preoperative planning for revision total hip arthroplasty.

Revision total hip arthroplasty is associated with more perioperative complications and unexpected findings than are encountered during primary total hip arthroplasty. Special instruments, implants, bone grafts, and other accessories may be required to treat complex problems that arise during revision surgery. Preoperative planning is important to anticipate potential complications and to ensure that all possible needed materials are readily available during surgery. Patients and their families also should be counseled on the specific additional risk factors involved in this complex surgery. An organized approach to revision total hip arthroplasty helps to reduce surgical time, minimize risks, decrease the stress level of the entire surgical team, and to increase the rate of successful outcomes for patients.

Resection arthroplasty: when enough is enough.

Resection arthroplasty following THA is rarely performed but occasionally indicated. It is a relatively low risk procedure and generally is a much shorter operative procedure associated with fewer perioperative complications compared to major revision procedures. Results are extremely variable. With all of the arthroplasty and bone graft options available for hip joint reconstruction, resection arthroplasty rarely is performed as a definitive procedure. It is, however, the best option for selected patients.

Extensor mechanism allograft reconstruction after total knee arthroplasty.

BACKGROUND: Disruption of the extensor mechanism is an uncommon but catastrophic complication of total knee arthroplasty. We evaluated two techniques of reconstructing a disrupted extensor mechanism with the use of an extensor mechanism allograft in revision total knee arthroplasty. METHODS: Twenty consecutive reconstructions with the use of an extensor mechanism allograft consisting of the tibial tubercle, patellar tendon, patella, and quadriceps tendon were performed. The first seven reconstructions (Group I) were done with the allograft minimally tensioned. The thirteen subsequent procedures (Group II) were performed with the allograft tightly tensioned in full extension. All surviving allografts were evaluated clinically and radiographically after a minimum duration of follow-up of twenty-four months. RESULTS: All of the reconstructions in Group I were clinical failures, with an average postoperative extensor lag of 59 degrees (range, 40 degrees to 80 degrees ) and an average postoperative Hospital for Special Surgery knee score of 52 points. All thirteen reconstructions in Group II were clinical successes, with an average postoperative extensor lag of 4.3 degrees (range, 0 degrees to 15 degrees ) (p < 0.0001) and an average Hospital for Special Surgery score of 88 points. Postoperative flexion did not differ significantly between Group I (average, 108 degrees ) and Group II (average, 104 degrees ) (p = 0.549). CONCLUSIONS: The results of reconstruction with an extensor mechanism allograft after total knee arthroplasty depend on the initial tensioning of the allograft. Loosely tensioned allografts result in a persistent extension lag and clinical failure. Allografts that are tightly tensioned in full extension can restore active knee extension and result in clinical success. On the basis of the number of knees that we studied, there was no significant loss of flexion. Use of an extensor mechanism graft for the treatment of a failure of the extensor mechanism will be successful only if the graft is initially tensioned tightly in full extension.

Pyoderma Gangrenosum in Revision Total Hip Arthroplasty: Clinical and Histopathological Findings with a Seven-Year Follow-up: A Case Report.

CASE: We describe the clinical and histopathological findings associated with a case of pyoderma gangrenosum (PG) after revision total hip arthroplasty. The patient developed an expanding purple-red, necrotic, ulcerative lesion at the surgical site, which was initially suspected to be either a surgical-site infection or warfarin-induced skin necrosis. After treatment with empiric intravenous antibiotics, surgical debridement, and vacuum-assisted closure of the wound, the patient had a painless hip with a remodeled scar and was asymptomatic at the seven-year follow-up. CONCLUSION: Confirmation of the diagnosis of surgical-site PG requires clinical-pathological correlation and familiarity with the PG skin lesion. Treatment of PG differs from treatment of infection; therefore, misdiagnosis and surgical treatment may exacerbate the clinical findings in PG.

Extensor mechanism allograft reconstruction after total knee arthroplasty. A comparison of two techniques.

BACKGROUND: Disruption of the extensor mechanism is an uncommon but catastrophic complication of total knee arthroplasty. We evaluated two techniques of reconstructing a disrupted extensor mechanism with use of an extensor mechanism allograft following total knee arthroplasty. METHODS: Twenty consecutive reconstructions with use of an extensor mechanism allograft consisting of the tibial tubercle, patellar tendon, patella, and quadriceps tendon were performed. The first seven reconstructions (Group I) were done with the allograft minimally tensioned. The thirteen subsequent procedures (Group II) were performed with the allograft tightly tensioned in full extension. All surviving allografts were evaluated clinically and radiographically after a minimum duration of follow-up of twenty-four months. RESULTS: All of the reconstructions in Group I were clinical failures, with an average postoperative extensor lag of 59 degrees (range, 40 degrees to 80 degrees ) and an average postoperative Hospital for Special Surgery knee score of 52 points. All thirteen reconstructions in Group II were clinical successes, with an average postoperative extensor lag of 4.3 degrees (range, 0 degrees to 15 degrees ) (p < 0.0001) and an average Hospital for Special Surgery score of 88 points. Postoperative flexion did not differ significantly between Group I (average, 108 degrees ) and Group II (average, 104 degrees ) (p = 0.549). CONCLUSIONS: The results of reconstruction with an extensor mechanism allograft after total knee arthroplasty depend on the initial tensioning of the allograft. Loosely tensioned allografts result in a persistent extension lag and clinical failure. Allografts that are tightly tensioned in full extension can restore active knee extension and result in clinical success. On the basis of the number of knees that we studied, there was no significant loss of flexion. Use of an extensor mechanism graft for the treatment of a failure of the extensor mechanism will be successful only if the graft is initially tensioned tightly in full extension. LEVEL OF EVIDENCE: Therapeutic study, Level III-2 (retrospective cohort study). See Instructions to Authors for a complete description of levels of evidence.

Assessment and classification of bone stock deficiency in revision total hip arthroplasty.

It is critical for appropriate treatment choices in revision total hip arthroplasty that bone stock deficiency be assessed and classified. Acetabular and femoral defects must be separately assessed, although a combined assessment is needed at the time of surgery to select the appropriate match of components for a given patient. Classification systems help surgeons predict defects and determine reconstruction planning prior to surgery. This article presents the senior author's classification of acetabular and femoral defects for revision total hip arthroplasty.

Extensively porous-coated femoral stems in revision hip arthroplasty: rationale and results.

Optimal outcomes of revision femoral arthroplasty include achieving rotational stability of the revision implant, preventing axial migration of the implant to obtain stability, and reproducing normal hip biomechanics. Cemented and proximally porous-coated implants are not well-suited to achieving these goals in the presence of metaphyseal bone defects and poor endosteal cement bonding. Extensively porous-coated implants are more likely to achieve these goals if the selection of the implant is appropriate for each defect encountered and if technical problems can be identified that may arise during canal preparation andcomponent insertion. The selection of curved implants for longer revisions may help avoid complications.

The value of intraoperative Gram stain in revision total knee arthroplasty.

BACKGROUND: The accurate preoperative diagnosis of infection is an essential component of decision-making prior to revision total knee arthroplasty. When preoperative modalities used to detect infection reveal equivocal findings, the surgeon may rely on intraoperative testing. While intraoperative Gram stains are routinely performed during revision total knee arthroplasty, their value remains unclear. METHODS: We retrospectively reviewed the records on 945 revision total knee arthroplasties performed at three university institutions to which patients were referred for total joint arthroplasty; the results of an intraoperative Gram stain were available for review in 921 cases (97.5%). Of these knees, 247 were classified as infected on the basis of (1) the presence of the same organism in two cultures; (2) growth, on solid media, of an organism as well as other objective evidence of infection; (3) histologic evidence of acute inflammation; (4) gross purulence; and/or (5) an actively draining sinus. We reviewed the results of preoperative laboratory studies, which included measurements of the erythrocyte sedimentation rate, C-reactive protein values, and white blood-cell count in 90%, 76%, and 98% of cases, respectively. Preoperative aspiration to obtain a specimen for culture and a cell count was performed routinely at one center and selectively at the other two centers, and the results were available for review in 439 (48%) of the 921 cases. RESULTS: Intraoperative Gram staining was found to have a sensitivity of 27% and a specificity of 99.9%. The positive and negative predictive values were 98.5% and 79%, respectively. The test accuracy was 80%. Patients with a true-positive Gram stain had a significantly higher preoperative white blood-cell count, C-reactive protein level, and nucleated cell count in the aspirate when compared with patients with a false-negative Gram stain (p < 0.001). In no case did the results of the intraoperative Gram stain alter treatment. CONCLUSIONS: The intraoperative Gram stain was found to have poor sensitivity and a poor negative predictive value, and its results did not alter the treatment of any patient undergoing revision total knee arthroplasty because of a suspected infection. These data do not support the routine use of intraoperative Gram staining in revision total knee arthroplasty; instead, they suggest a much more limited role for this test.

Patellar resurfacing compared with nonresurfacing in total knee arthroplasty. A concise follow-up of a randomized trial.

Patellar resurfacing in total knee arthroplasty remains controversial. This study compared the long-term clinical outcomes of total knee arthroplasties performed with and without the patella resurfaced and is an update of a previous report. Eighty-six patients (118 knees) underwent primary total knee replacement and were randomized into two groups: those treated with and those treated without resurfacing of the patella. Outcomes included the scores according to the Knee Society clinical rating system, the scores according to a forty-one-question patellofemoral-specific patient questionnaire, patient satisfaction, global and anterior knee pain scores, radiographic findings, and complications and revisions. Fifty-seven patients (seventy-eight knees) were followed for a minimum of ten years. No significant differences were identified between the two groups in terms of the range of motion, Knee Society scores, satisfaction, global knee pain, or anterior knee pain. The overall revision rates in the original series of 118 knees were 12% in the nonresurfacing group and 9% in the resurfacing group. Seven patients (12%) in the nonresurfacing group and two patients (3%) in the resurfacing group underwent revision for a reason related to a patellofemoral problem. On the basis of these findings, we concluded that, with the type of total knee arthroplasty used in our patients, similar results may be achieved with and without patellar resurfacing.

Revision total knee arthroplasty for major osteolysis.

Twenty-eight knees in 26 patients underwent revision TKA requiring surgical management of major osteolytic defects. Three groups of osteolytic defects were identified based upon the degree of implant stability and the magnitude of bone loss. Outcome measures included the Knee Society Clinical Rating Score (KSCRS), visual analog pain score, and radiographs. At a mean follow-up of 48 months, the average knee pain scores, range of motion, and KSCRS improved (p<.05). Ninety-six percent of the knees demonstrated clinical and functional improvement. Radiographs for 24 revision TKA's (86 percent) demonstrated component stability and incorporation of both cancellous and structural allografts. Revision TKA for major osteolytic defects may be effectively performed using a variety of bone grafting techniques. Both morselized and structural bone grafting, in combination with stemmed components was successful in managing revision TKA in the setting of major osteolysis. Significant improvement in clinical and radiographic outcomes may be anticipated using these surgical techniques.

Cell count and differential of aspirated fluid in the diagnosis of infection at the site of total knee arthroplasty.

BACKGROUND: Although there is no absolute diagnostic test for periprosthetic infection, the synovial fluid leukocyte count and neutrophil percentage have been reported to have high sensitivity and specificity. However, the cutoff values for these tests are not agreed upon. We sought to identify definite cutoff values for both the fluid leukocyte count and the neutrophil percentage that may help to diagnose infection at the site of a prosthetic joint. METHODS: We analyzed synovial fluid that had been aspirated preoperatively from 429 knees that had undergone revision arthroplasty at three different academic institutions; 161 knees were found to be infected, and 268 knees were not. Using receiver operating characteristic curves, we determined cutoff values for the fluid leukocyte count and neutrophil differential with an optimal balance of sensitivity and specificity for the diagnosis of periprosthetic infection. The sensitivity, specificity, and predictive values were calculated for those cutoff values. The erythrocyte sedimentation rate and C-reactive protein level cutoff values of 30 mm/hr and 10 mg/L, respectively, were combined with the cutoff values for the fluid leukocyte count and neutrophil percentage. RESULTS: The cutoff values for optimal accuracy in the diagnosis of infection were >1100 cells/10(-3)cm(3) for the fluid leukocyte count and >64% for the neutrophil differential. When both tests yielded results below their cutoff values, the negative predictive value of the combination increased to 98.2% (95% confidence interval, 95.5% to 99.5%), whereas when both tests yielded results greater than their cutoff values, infection was confirmed in 98.6% (95% confidence interval, 94.9% to 99.8%) of the cases in our cohort. Similarly, when both the neutrophil percentage and the C-reactive protein level were less than the cutoff values of 64% and 10 mg/L, respectively, the presence of periprosthetic infection was very unlikely. CONCLUSIONS: The synovial fluid leukocyte count and differential are useful adjuncts to the erythrocyte sedimentation rate and the C-reactive protein level in the preoperative workup of infection at the site of a total knee arthroplasty. The present study identified cutoff values for the leukocyte count (>1100 cells/10(-3)cm(3)) and neutrophil percentage (>64%) that can be used to diagnose infection. Combining the peripheral blood tests with the synovial fluid cell count and differential can improve their diagnostic value.