The Microbiology of Knee Prosthetic Joint Infection and its Influence on Persistent Infection.

Periprosthetic joint infection (PJI) following total knee arthroplasty (TKA) is a severe complication causing a significant burden. The study aims were to establish the epidemiology of microorganisms in TKA PJI, the rate of persistent infection requiring further surgery, and the risk factors for this. Microbiological specimens between June 2002 and March 2017 at five regional hospital sites were identified with revision TKA procedures in the National Joint Replacement Registry. The time between procedures, type of revision strategy, and any subsequent further revision operations were collected. At minimum 2-year follow-up, 174 revision TKA were identified, with a mean patient age of 69 ± 11 years. A broad range of pathogens were identified. Fifty cases (29%) had persistent infection requiring at least one further operative procedure, 13 cases required 3 or more. Coagulase-negative Staphylococcus species (CNS) was seen most with failed surgery, polymicrobial infections also posing a significant risk factor. The best chance of a successful PJI surgical strategy was < 12 months from primary TKA, with the greatest risk between 3 and 5 years (p < 0.05). Younger age significantly increased the risk of further surgery (p < 0.05). Management varied; 103 (59%) debridement, antibiotic therapy and implant retention, with further surgery in 29%; 45 (17%) single-stage revision, with further surgery in 13%; and 26 (15%) two-stage revision, with further surgery in 12%. This study presents the most common causative pathogens for PJI in TKA, and the high rate of persistent infection after initial revision surgery. Risk factors for persistent infection and further revision surgery were polymicrobial and CNS infections, patients who presented between 3 and 5 years following primary TKA, and younger age. This study therefore raises important risk factors and areas for future research to reduce the burden of multiple operations after PJI.

Level-specific comparison of 3D navigated and robotic arm-guided screw placement: an accuracy assessment of 1210 pedicle screws in lumbar surgery.

BACKGROUND CONTEXT: Robotic spine surgery, utilizing 3D imaging and robotic arms, has been shown to improve the accuracy of pedicle screw placement compared to conventional methods, although its superiority remains under debate. There are few studies evaluating the accuracy of 3D navigated versus robotic-guided screw placement across lumbar levels, addressing anatomical challenges to refine surgical strategies and patient safety. PURPOSE: This study aims to investigate the pedicle screw placement accuracy between 3D navigation and robotic arm-guided systems across distinct lumbar levels. STUDY DESIGN: A retrospective review of a prospectively collected registry PATIENT SAMPLE: Patients undergoing fusion surgery with pedicle screw placement in the prone position, using either via 3D image navigation only or robotic arm guidance OUTCOME MEASURE: Radiographical screw accuracy was assessed by the postoperative computed tomography (CT) according to the Gertzbein-Robbins classification, particularly focused on accuracy at different lumbar levels. METHODS: Accuracy of screw placement in the 3D navigation (Nav group) and robotic arm guidance (Robo group) was compared using Chi-squared test/Fisher's exact test with effect size measured by Cramer's V, both overall and at each specific lumbosacral spinal level. RESULTS: A total of 321 patients were included (Nav, 157; Robo, 189) and evaluated 1210 screws (Nav, 651; Robo 559). The Robo group demonstrated significantly higher overall accuracy (98.6 vs. 93.9%; p<.001, V=0.25). This difference of no breach screw rate was signified the most at the L3 level (No breach screw: Robo 91.3 vs. 57.8%, p<.001, V=0.35) followed by L4 (89.6 vs. 64.7%, p<.001, V=0.28), and L5 (92.0 vs. 74.5%, p<.001, V=0.22). However, screw accuracy at S1 was not significant between the groups (81.1 vs. 72.0%, V=0.10). CONCLUSION: This study highlights the enhanced accuracy of robotic arm-guided systems compared to 3D navigation for pedicle screw placement in lumbar fusion surgeries, especially at the L3, L4, and L5 levels. However, at the S1 level, both systems exhibit similar effectiveness, underscoring the importance of understanding each system's specific advantages for optimization of surgical complications.

Limited Improvement With Minimally Invasive Lumbar Decompression Alone for Degenerative Scoliosis With Cobb Angle Over 20°: The Impact of Decompression Location.

STUDY DESIGN: Retrospective review of a prospectively collected multisurgeon registry. OBJECTIVE: To evaluate the outcomes of minimally invasive (MI) decompression in patients with severe degenerative scoliosis (DS) and identify factors associated with poorer outcomes. SUMMARY OF BACKGROUND CONTEXT: MI decompression has gained widespread acceptance as a treatment option for patients with lumbar canal stenosis and DS. However, there is a lack of research regarding the clinical outcomes and the impact of MI decompression location in patients with severe DS exhibiting a Cobb angle exceeding 20°. MATERIALS AND METHODS: Patients who underwent MI decompression alone were included and categorized into the DS or control groups based on Cobb angle (>20°). Decompression location was labeled as "scoliosis-related" when the decompression levels were across or between end vertebrae and "outside" when the operative levels did not include the end vertebrae. The outcomes, including the Oswestry Disability Index (ODI), were compared between the propensity score-matched groups for improvement and minimal clinical importance difference (MCID) achievement at ≥1 year postoperatively. Multivariable regression analysis was conducted to identify factors contributing to the nonachievement of MCID in ODI of the DS group at the ≥1-year time point. RESULTS: A total of 253 patients (41 DS) were included in the study. Following matching for age, sex, osteoporosis status, psoas muscle area, and preoperative ODI, the DS groups exhibited a significantly lower rate of MCID achievement in ODI (DS: 45.5% vs. control 69.0%, P =0.047). The "scoliosis-related" decompression (odds ratio: 9.9, P =0.028) was an independent factor of nonachievement of MCID in ODI within the DS group. CONCLUSIONS: In patients with a Cobb angle >20°, lumbar decompression surgery, even in the MI approach, may result in limited improvement of disability and physical function. Caution should be exercised when determining a surgical plan, especially when decompression involves the level between or across the end vertebrae. LEVEL OF EVIDENCE: 3.

The Impact of Posterior Intervertebral Osteophytes on Patient-Reported Outcome Measures After L5-S1 Anterior Lumbar Interbody Fusion and Transforaminal Lumbar Interbody Fusion.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: (1) To develop a reliable grading system to assess the severity of posterior intervertebral osteophytes and (2) to investigate the impact of posterior intervertebral osteophytes on clinical outcomes after L5-S1 decompression and fusion through anterior lumbar interbody fusion (ALIF) and minimally-invasive transforaminal lumbar interbody fusion (MIS-TLIF). BACKGROUND: There is limited evidence regarding the clinical implications of posterior lumbar vertebral body osteophytes for ALIF and MIS-TLIF surgeries and there are no established grading systems that define the severity of these posterior lumbar intervertebral osteophytes. PATIENTS AND METHODS: A retrospective analysis of patients undergoing L5-S1 ALIF or MIS-TLIF was performed. Preoperative and postoperative patient-reported outcome measures of the Oswestry Disability Index (ODI) and leg Visual Analog Scale (VAS) at 2-week, 6-week, 12-week, and 6-month follow-up time points were assessed. Minimal clinically important difference (MCID) for ODI of 14.9 and VAS leg of 2.8 were utilized. Osteophyte grade was based on the ratio of osteophyte length to foraminal width. "High-grade" osteophytes were defined as a maximal osteophyte length >50% of the total foraminal width. RESULTS: A total of 70 consecutive patients (32 ALIF and 38 MIS-TLIF) were included in the study. There were no significant differences between the two cohorts in patient-reported outcome measures or achievement of MCID for Leg VAS or ODI preoperatively or at any follow-ups. On multivariate analysis, neither the surgical approach nor the presence of high-grade foraminal osteophytes was associated with leg VAS or ODI scores at any follow-up time point. In addition, neither the surgical approach nor the presence of high-grade foraminal osteophytes was associated with the achievement of MCID for leg VAS or ODI at 6 months. CONCLUSION: ALIF and MIS-TLIF are both valid options for treating degenerative spine conditions and lumbar radiculopathy, even in the presence of high-grade osteophytes that significantly occupy the intervertebral foramen. LEVEL OF EVIDENCE: 3.

Magnetic Resonance Imaging Assessment of Hamstring Graft Healing and Integration 1 and Minimum 2 Years after ACL Reconstruction.

BACKGROUND: An increase has been seen in the number of studies of anterior cruciate ligament reconstruction (ACLR) that use magnetic resonance imaging (MRI) as an outcome measure and proxy for healing and integration of the reconstruction graft. Despite this, the MRI appearance of a steady-state graft and how long it takes to achieve such an appearance have not yet been established. PURPOSE: To establish whether a hamstring tendon autograft for ACLR changes in appearance on MRI scans between 1 and 2 years and whether this change affects a patient's ability to return to sports. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Patients with hamstring tendon autograft ACLR underwent MRI and clinical outcome measures at 1 year and at a final follow-up of at least 2 years. MRI graft signal was measured at multiple regions of interest using oblique reconstructions both parallel and perpendicular to the graft, with lower signal indicative of better healing and expressed as the signal intensity ratio (SIR). Changes in tunnel aperture areas were also measured. Clinical outcomes were side-to-side anterior laxity and patient-reported outcome measures (PROMs). RESULTS: A total of 42 patients were included. At 1 year, the mean SIR for the graft was 2.7 ± 1.2. Graft SIR of the femoral aperture was significantly higher than that of the tibial aperture (3.4 ± 1.3 vs 2.6 ± 1.8, respectively; P = .022). Overall, no significant change was seen on MRI scans after 2 years; a proximal graft SIR of 1.9 provided a sensitivity of 96% to remain unchanged. However, in the 6 patients with the highest proximal graft SIR (>4) at 1 year, a significant reduction in signal was seen at final follow-up (P = .026), alongside an improvement in sporting level. A significant reduction in aperture area was also seen between 1 and 2 years (tibial, -6.3 mm2, P < .001; femoral, -13.3 mm2, P < .001), which was more marked in the group with proximal graft SIR >4 at 1 year and correlated with a reduction in graft signal. The patients had a high sporting level; the median Tegner activity score was 6 (range, 5-10), and a third of patients scored either 9 or 10. Overall, PROMs and knee laxity were not associated with MRI appearance. CONCLUSION: In the majority of patients, graft SIR on MRI did not change significantly after 1 year, and a proximal graft SIR <2 was a sensitive indicator for a stable graft signal, implying healing. Monitoring is proposed for patients who have a high signal at 1 year (proximal graft SIR >4), because a significant reduction in signal was seen in the second year, indicative of ongoing healing, alongside an improvement in sporting level. A reduction in tunnel aperture area correlated with a reduction in graft SIR, suggesting this could also be a useful measure of graft integration.

Abnormal lymphatic phenotype in a CRISPR mouse model of the human lymphedema-causing Connexin47 R260C point mutation.

Connexin proteins form gap junctions controlling exchange of ions and small molecules between cells and play an important role in movement of lymph within lymphatic vessels. Connexin47 (CX47) is highly expressed in lymphatic endothelial cells and CX47 missense mutations, i.e., R260C, cosegregate with primary lymphedema in humans. However, studies utilizing CX47 knockout mice have failed to demonstrate any lymphatic anomalies. To unravel the lymphatic consequences of expressing a mutant CX47 protein, we used CRISPR technology to create a mouse carrying a Cx47 missense mutation (Cx47R259C) equivalent to the human CX47R260C missense mutation associated with human primary lymphedema. Intradermal Evans Blue dye injection identified a 2-fold increase in regional lymph nodes in homozygous Cx47R259C mice compared to wildtype, particularly in the jugular region (4.8 ± 0.4 and 2.0 ± 0.0, respectively, p<0.01). Associated lymphatic channels were increased in Cx47R259C mice and mesenteric lymph reflux occurred in homozygous Cx47R259C mice but not in wildtype. Contractility of superficial cervical lymphatics, assessed by pressure myography, was reduced in homozygous Cx47R259C mice compared to wildtype. In conclusion, our data are the first to demonstrate a role for the Cx47 protein in lymphatic anatomy and function. This phenotype is similar to that found with other valve deficient mouse mutants, e.g., in Foxc2. Of significance, this study is the first to use CRISPR technology to develop a pre-clinical model of primary lymphedema and demonstrates the importance of distinguishing between lack of and presence of mutant protein when developing clinically relevant animal models for translation of pre-clinical findings.

Adjustable suspension versus hybrid fixation in hamstring autograft anterior cruciate ligament reconstruction.

BACKGROUND: There has been increased use of adjustable suspensory fixation (ASF) for anterior cruciate ligament reconstruction (ACLR). Potential benefits are the ability to use a shorter graft and to prevent graft displacement and damage. The purpose of this study was to establish the efficacy of this fixation method and assess whether it leads to less tunnel widening, and avoids known complications of screw fixation. METHODS: Thirty-eight patients who underwent ACLR with ASF on both the femoral and tibial sides met the inclusion criteria and were propensity matched demographically with 38 patients who underwent hybrid fixation with femoral suspensory and tibial screw and sheath. At one-year, KT-1000 knee laxity measurements were recorded and detailed MRI analysis looking at tunnel aperture widening, tunnel appearance, graft integration within the tunnels, and graft healing. RESULTS: MRI comparison between ASF and hybrid cohorts revealed no significant differences in graft signal or integration, and clinically there were no differences in knee laxity between cohorts (mean 1.5 mm ± 2.0 and 1.5 mm ± 2.3 (n.s.) in the ASF and hybrid fixation respectively). Significantly less aperture tibial tunnel widening (2.2 mm versus 4.4 mm, p < 0.0001) and tibial cysts (2 versus 9, p = 0.047) were observed in the ASF cohort, whilst mean femoral tunnel widening was comparable between both cohorts (ASF 2.8 mm, hybrid 3.2 mm; n.s.). CONCLUSIONS: Hamstring autografts for ACLR fixed using either ASF or a hybrid fixation technique provided comparable knee stability and MRI graft signal intensity. Tibial ASF demonstrated significantly less tibial aperture widening and tunnel cyst formation when compared to screw and sheath fixation.

Total Knee Arthroplasty in a Transtibial Amputee.

INTRODUCTION: With the diversity of prosthetic components patients with a transtibial amputation can now expect to return to high function. Subsequently, the ipsilateral knee is at risk of developing osteoarthritis with a need for a provision of total knee arthroplasty (TKA). CASE REPORT: We describe a novel technique for TKA in a transtibial amputee utilizing navigation with a tibial jig. Post-operative radiographs revealed varus tibial alignment with neutral limb alignment. Resolution of stump swelling allowing accurate prosthesis fitting was seen at 8 weeks. A new prosthesis optimized functional alignment and a return to moderate labor was achieved at 10 weeks. At 1-year postoperatively, patient satisfaction was excellent. CONCLUSION: Navigation alongside stump alignment is a useful technique. We found that after socket fitting, radiographic tibial varus alignment can correspond with a stump position that allows balanced loading of the knee and excellent function.

One-Stage Sequential Bilateral Total Knee Arthroplasty: An Effective Treatment for Advanced Bilateral Knee Osteoarthritis Providing High Patient Satisfaction.

BACKGROUND: The mortality and risks of bilateral total knee arthroplasty (BTKA) have been reported to be far greater than in unilateral total knee arthroplasty (UTKA). This study aimed to determine whether this remains the case using contemporary anesthetic and surgical techniques for one-stage single anesthetic sequential BTKA. METHODS: Two cohorts of 394 patients were created by propensity matching for gender, age, body mass index, American Society of Anesthesiologists grade, and Veterans Rand-12 health survey scores. Primary outcome was morbidity and mortality, with satisfaction measures using patient-reported outcome measures. RESULTS: The mortality rate was low with one case after BTKA. Major complications were also low; however, a pulmonary embolism rate of 2% in BTKA patients was significantly higher than 0.3% after UTKA (P < .05), and associated with an American Society of Anesthesiologists grade ≥3. The rate of minor complications between the 2 cohorts was comparable (P = .95). Blood transfusions were uncommon and not significantly different between cohorts (2.5% vs 1.3%, P = .3). BTKA patients stayed in hospital a mean 1.3 days longer with greater rehabilitation requirements. At final follow-up, patient satisfaction was high with all patient-reported outcome measures significantly improved and comparable between cohorts. CONCLUSION: BTKA is safe and effective in the majority of patients. Transfusion rates were far lower than historically reported and major complications were rare after both UTKA and BTKA. A significant increase in the rate of pulmonary embolism after BTKA was observed, especially in high risk patients. At minimum 1-year postoperatively, cohorts had the same significant clinical improvement and high level of satisfaction.

Lack of agreement between computer navigation and post-operative 2-dimensional computed tomography (CT) measurements for component and limb alignment in total knee arthroplasty (TKA).

BACKGROUND: The purpose of this study was to assess the degree of mismatch between intraoperative navigation data using imageless computer navigation and post-operative CT scan measurements with respect to bone cuts, component and limb alignment during TKA. METHODS: Intraoperative navigation data including bone cut verification and overall limb alignment during TKA was compared to postoperative CT measurements of component and limb alignment according to the Perth protocol. The proportion of cases with mismatch between navigation and CT measurements at two and three degree thresholds was identified. RESULTS: In a total sample of 50 primary TKAs, 20% of cases showed a mismatch of more than two degrees between navigation and CT obtained measurements for coronal femoral alignment, 42% for femoral rotation, 16% for tibial component coronal alignment and 32% for overall limb alignment. CONCLUSION: Mismatch between intraoperative navigation data and postoperative CT measurements suggests that postoperative CT scan alignment data should be interpreted with caution. A surgeon should consider a multitude of factors when analysing component and limb alignment postoperatively.

Patient-specific instrumentation for total knee arthroplasty does not match the pre-operative plan as assessed by intra-operative computer-assisted navigation.

PURPOSE: The introduction of patient-specific instruments (PSI) for guiding bone cuts could increase the incidence of malalignment in primary total knee arthroplasty. The purpose of this study was to assess the agreement between one type of patient-specific instrumentation (Zimmer PSI) and the pre-operative plan with respect to bone cuts and component alignment during TKR using imageless computer navigation. METHODS: A consecutive series of 30 femoral and tibial guides were assessed in-theatre by the same surgeon using computer navigation. Following surgical exposure, the PSI cutting guides were placed on the joint surface and alignment assessed using the navigation tracker. The difference between in-theatre data and the pre-operative plan was recorded and analysed. RESULTS: The error between in-theatre measurements and pre-operative plan for the femoral and tibial components exceeded 3° for 3 and 17% of the sample, respectively, while the error for total coronal alignment exceeded 3° for 27% of the sample. CONCLUSION: The present results indicate that alignment with Zimmer PSI cutting blocks, assessed by imageless navigation, does not match the pre-operative plan in a proportion of cases. To prevent unnecessary increases in the incidence of malalignment in primary TKR, it is recommended that these devices should not be used without objective verification of alignment, either in real-time or with post-operative imaging. Further work is required to identify the source of discrepancies and validate these devices prior to routine use. LEVEL OF EVIDENCE: II.

Incidence and severity of complications due to femoral nerve blocks performed for knee surgery.

BACKGROUND: While single shot femoral nerve blocks and indwelling femoral nerve catheters provide significant peri-operative analgesia, there are small but serious risks of neurovascular complications. We aimed to determine the incidence and characterise the nature of neural complications arising from femoral nerve blocks performed for knee surgery. METHODS: One thousand eight hundred and two patients receiving a femoral nerve block for knee surgery during the study period were screened. Patients with possible neurological symptoms were evaluated with a detailed physical examination and self-report questionnaires. Also measures of depression, anxiety and tension/stress were collected. RESULTS: In the patients screened, an incidence of 1.94% was found. Of the 24 patients available for testing, 4 had bilateral symptoms following bilateral nerve blocks. All had sensory abnormalities in the distribution of the femoral nerve. The incidence was significantly higher in females (females=2.5%, males=0.83% p=0.01) and in patients receiving a single shot block (single shot=2.66%, femoral catheter=0.93, p=0.01). CONCLUSIONS: The incidence of neurological complication after FNB was higher in this series than typically reported and the symptoms significantly influenced the quality of life in the affected cases. The decision to include a femoral nerve block in the peri-operative analgesic regimen should be made on an individual basis considering the risks and benefits.

Unsatisfactory accuracy as determined by computer navigation of VISIONAIRE patient-specific instrumentation for total knee arthroplasty.

This investigation evaluated the Smith and Nephew VISIONAIRE patient-specific cutting block (PSCB) system for total knee arthroplasty. A consecutive series of 60 patients was recruited. Intraoperative computer navigation was used to evaluate the accuracy of the cutting blocks in the coronal and sagittal planes for the tibia, as well as rotational plane for the femur. The PSCB would have placed 79.3% of the sample within ±3° of the preoperative plan in the coronal plane, while the rotational and sagittal alignment results within ±3° were 77.2% and 54.5% respectively. The VISIONAIRE PSCB system achieved unacceptable accuracy when assessed by computer navigation. There might be many sources of error, but caution is recommended before using this system routinely without objective verification of alignment.

Is femoral nerve block necessary during total knee arthroplasty?: a randomized controlled trial.

There remains a lack of randomized controlled trials comparing methods of perioperative analgesia for total knee arthroplasty. To address this deficiency, a blinded, randomized controlled trial was conducted to compare the use of femoral nerve block (group F) and local anesthetic (group L). A sample of 55 patients who met the inclusion criteria were randomized to either group. No significant differences in the most severe pain score or 36-Item Short Form Health Survey, The Western Ontario and McMaster Universities Arthritis Index (WOMAC), or Oxford scores were observed between groups. However, the Knee Society score was significantly higher in group F. In addition, group F used significantly fewer micrograms of intravenous fentanyl in the first 24 hours. Balancing the risks of femoral nerve block with those of increased systemic narcotic delivery should be performed on a case-by-case basis.

Sagittal placement of the femoral component in total knee arthroplasty predicts knee flexion contracture at one-year follow-up.

PURPOSE: Flexion contracture has been shown to impair function and reduce satisfaction following total knee arthroplasty (TKA). The aim of this study was to identify modifiable intra-operative variables that predict post-TKA knee extension. METHODS: Data was collected prospectively on 95 patients undergoing total knee arthroplasty, including pre-operative assessment, intra-operative computer assisted surgery (CAS) measurements and functional outcome including range of motion at one year. Patients were divided into two groups: those with mild flexion contracture (> 5°) at the one-year follow-up and those achieving full extension. RESULTS: The sagittal orientation of the distal femoral cut differed significantly between groups at the one-year follow-up (p = 0.014). Sagittal alignment of greater than 3.5° from the mechanical axis was shown to increase the relative risk of a mild flexion contracture at one-year follow-up by 2.9 times, independent of other variables. CONCLUSION: Increasing the sagittal alignment of the distal femoral cut more than 3.5° from the mechanical axis is an independent risk factor for clinically detectable flexion contracture one year from index procedure.

Tibial fixation in anterior cruciate ligament reconstruction: a prospective randomized study comparing metal interference screw and staples with a centrally placed polyethylene screw and sheath.

BACKGROUND: The use of hamstring tendons for anterior cruciate ligament reconstruction has increased in popularity over recent years. However, concerns with the stability of graft fixation on the tibial side remain. Centrally placed interference screw/sheath implants have demonstrated promising results in biomechanical studies. HYPOTHESIS: Centrally placed, polyethylene screw and sheath implants will provide clinically equivalent fixation to the standard metal interference screw and supplemental staple fixation. STUDY DESIGN: Randomized controlled trial; Level of evidence, 1. METHODS: A total of 113 consecutive patients undergoing isolated, unilateral, primary anterior cruciate ligament reconstruction with hamstring autografts were randomized to tibial fixation with metal interference screw and staples (RCI) or with a centrally placed polyethylene screw and sheath implant (INTRAFIX). Prospective assessment of subjective outcomes was performed using Lysholm, Mohtadi, and International Knee Documentation Committee (IKDC) scores. RESULTS: At minimum 2-year follow-up, there were no significant differences between the 2 groups in terms of instrumented stability testing (KT-1000 arthrometer) or subjective assessment of knee outcomes (IKDC, Lysholm, Mohtadi). Both fixation methods demonstrated a significant, but not different, increase in outcomes scores from preoperative to postoperative evaluation. There were 7 failures (5 INTRAFIX, 2 RCI) caused by reinjury, but no statistically significant differences were observed between the 2 fixation methods. CONCLUSION: The centrally placed polyethylene screw and sheath provided equivalent clinical outcomes at minimum 2-year follow-up to standard tibial fixation with metal interference screw and staples.

Articular cartilage changes in patients with osteoarthritis after osteotomy.

BACKGROUND: High tibial osteotomy (HTO) is a method used to treat medial compartmental osteoarthritis in the knee. The realignment of the knee changes the loading patterns within the joint and may allow for regeneration of articular cartilage. Magnetic resonance imaging methods can be used to assess the quality of the regenerated cartilage. HYPOTHESIS: Altering mechanical alignment through HTO will have predictable effects on articular cartilage, allowing cartilage preservation and possible regeneration. Quality of regenerated cartilage will be inferior to normal articular cartilage. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Ten patients undergoing medial opening wedge HTO were evaluated using dGEMRIC methods (ie, delayed gadolinium-enhanced magnetic resonance imaging of cartilage) preoperatively and at 6 months, 1 year, and 2 years after HTO. Magnetic resonance images were evaluated by hand segmentation, and T1(Gd) relaxation times reflective of glycosaminoglycan content were determined for these regions of interest using magnetic resonance imaging analysis software. RESULTS: The lateral compartment displayed higher T1(Gd) values than the medial compartment at baseline. Initially, a decrease in T1(Gd) values on the medial side were observed for all patients at 6 months and remained reduced for all but 2 participants at 1 year and 2 years after HTO. However, on the medial side after 6 months, the rate of change for T1(Gd) values shifted from being negative (-9.6 milliseconds per month) to being positive (1.7 milliseconds per month). A positive change in the T1(Gd) of the medial tibial plateau was responsible for the positive overall change in the medial compartment. There was no significant difference in the rate of change on the lateral side (P = .141), with the average over the 2-year period being a decrease of 2.28 milliseconds per month. CONCLUSION: Medial opening wedge HTO provides subjective improvements in pain and quality of life, but the potential benefit of allowing articular cartilage preservation and possible regeneration is not well established. Results showed that after a nonweightbearing period, the rate of change in the medial compartment changes from negative to positive, indicating the potential for articular cartilage recovery secondary to an improved mechanical environment.

The accuracy of magnetic resonance imaging scanning and its influence on management decisions in knee surgery.

PURPOSE: The purpose of our study was to evaluate the impact of preoperative magnetic resonance imaging (MRI) assessment of articular knee pathology on the clinical management of patients presenting with joint line pain. METHODS: A preliminary study on 100 patients was performed to assess the accuracy of specific MRI sequences, using arthroscopy as a gold standard. Six hundred and eighteen consecutive patients with knee symptoms presenting to 2 specialist knee surgeons were then recruited. A clinical diagnosis of an arthroscopically treatable lesion was made in all cases. Clinical assessment data were correlated to subsequent MRI findings, recording any discrepancy and in particular whether or not MRI findings influenced management decisions. RESULTS: In the preliminary study, MRI sequences had an overall sensitivity of 83.2% and a specificity of 94.3% for the detection of chondral lesions. However, when considering arthroscopic grade III and IV lesions, MRI sensitivity and specificity were improved to 84.5% and 97.1%. In the second phase of the study, 141 (22.8%) of the 618 patients presenting with knee symptoms had an altered clinical management subsequent to MRI. The presence of unexpected chondral lesions was found in 77 of these patients. Conversely, 22 patients with clinical symptoms suspicious for simple chondral degeneration had unstable meniscal tears. CONCLUSIONS: We suggest that preoperative MRI scanning identifies a group of patients who have more advanced degenerative joint disease than the clinical assessment and the plain radiographs suggest. This would expedite definitive surgery in patients with advanced osteoarthritis on MRI scans. LEVEL OF EVIDENCE: Level II, development of diagnostic criteria on basis of consecutive patients with universally applied gold standard.

Safety of combined use of local anesthetic infiltration and reinfusion drains in total knee arthroplasty.

Injection of local anesthetic during total knee arthroplasty (TKA) has been shown to aid postoperative pain relief. Reinfusion drains have also proven useful in decreasing allogenic blood transfusion. Combined use carries the risk of reinfusion of local anesthetic from drainage bag. We examined plasma ropivacaine concentrations from 20 patients undergoing TKA, who were treated with these 2 techniques. Samples were taken from a dedicated venous cannula and from the reinfusion drainage bag. The average amount of ropivacaine reinfused was 1.9 mg, a fraction of the injected dose (150 mg), and venous plasma concentrations reached peaks of 0.5 to 1.5 microg/mL, well below demonstrated levels of toxicity. Patients tolerated the treatment well, with no adverse outcomes. This study demonstrates the safety of combining these 2 techniques in TKA.