Anatomical risk factors for aseptic loosening of full hinge knee prosthesis in primary and revision TKAs.

INTRODUCTION: Risk factors (RF) associated with aseptic loosening (AL) in total knee arthroplasty (TKA) are poorly understood. Therefore, the aim of this study was to investigate the anatomical shape variations in relation to the inner-diameter of the femur and the tibia as prognostic RF for AL of full hinge prosthesis (FHP) in primary and revision TKA. MATERIALS AND METHODS: We retrospectively examined all patients, who underwent revision surgery (2003-2018) due to AL of the FHP in primary (n = 38) and revision TKA (n = 46). Diagnosis-appropriate controls without AL at minimum follow-up of 24 months were randomly collected for each group. Besides other risk factors, we also measured the inner diameter of the femur according to the Citak classification and of the tibia on anteroposterior radiographies. RESULTS: RF for AL are younger age in primary and revision as well as > 1 previous surgeries in revision TKA. The femoral index was shown to be a RF for AL in revision TKA (p = 0.001), but not in primary TKA. The novel tibial index was associated with AL in primary with AUC 0.776 (95% CI 0.67, 0.88), 65.8% sensitivity, 86.6% specificity and in revision TKA with AUC 0.817 (95% CI 0.73, 0.91), 82.6% sensitivity and 71.7% specificity. CONCLUSION: This is the first study to calculate the tibial measurements and the tibial index according to Citak et al. and to identify them as prognostic RF for AL of the full hinge knee prosthesis in TKA and confirm the femoral index as a RF for AL also in revision full hinge knee prosthesis. Therefore, the preoperative radiological evaluation should include the analysis of the anatomical shape variants in order to select the appropriate prosthesis design with a possibly enhanced prognosis.

Correlation between EFAS- and MOCART score and clinical outcome after AMIC®-procedure for osteochondral lesion of the talus.

INTRODUCTION: Even though an increased interest in the use of the EFAS Score (European Foot and Ankle Society) has been observed, no data comparing it with radiological findings has been presented in the literature. Accordingly, the aim of this study is to investigate how the post-operative integration of the AMIC® (autologous matrix-induced chondrogenesis)-membrane for osteochondral lesion of the talus using the MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) - Score is related to the clinical satisfaction of the patients. MATERIAL AND METHODS: A group of 24 patients aged between 17 and 63 (with a mean age of 35.7) were included at least 1 year post-operatively. They had all undergone an AMIC®-procedure of the talus. MRI findings using the MOCART Score were correlated to the EFAS Score at the same time point. RESULTS: Our main results showed no correlation between the MOCART-Score and the EFAS-Score (R = - 0.08). There was also no correlation between the MOCART-Score, the FFI-Score (Foot and Function Index) (R = 0.2) and the MOXFQ-Score (Manchester-Oxford Foot Questionnaire) (R = 0.12). There was no correlation between components of the MOCART-Score with the EFAS-Score (R between - 0.32 and 0.23). CONCLUSION: Our results question whether the MRI (a standard part of AMIC®-procedure-of-the-ankle post-operative follow-up) is still the most appropriate tool for post-operative control. They also offer a starting point for future discussion regarding the need for post-operative MRI and the use of other radiological diagnostics in relation to clinical satisfaction.

A novel radiological classification system of the distal femur.

INTRODUCTION: In our previous studies, we were able to identify anatomical differences as a predictor for aseptic loosening following primary and revision surgery with the use of rotating hinge prosthesis. This study was performed to answer following question: can a novel radiological classification system of the distal femur be identified? MATERIALS AND METHODS: A total of 200 patients who received standardized anteroposterior (AP) and lateral views of the knee joint were included in this study. On AP radiographs, we measured the distance between inner diameter of the femur at 20 cm proximally from the knee and at a point 2 cm proximally from the adductor tubercle. The ratio of the inner diameter of the femoral canal at 20 cm proximal of knee joint to the inner diameter of medullary canal at 2 cm proximal of adductor tubercle was used as a novel index ratio. Two observers blindly and independently reviewed the anteroposterior radiographs twice. RESULTS: Three groups of anatomical classification can be constructed for each sex according to the 25th and 75th percentiles. A higher distribution of Type C was found in female patients. The median intra-observer reliability for rater 1 was 0.995 (IQR 0.994-0.997). We had also a high inter-observer reliability with ICC of 0.997 (95% CI 0.996-0.998). CONCLUSIONS: The novel classification presents three different types of the knee joint for male and female patients. Type C has a wider inner diaphyseal diameter compared to Type A with a narrow inner diaphyseal diameter.

Radiographic cortical thickness parameters as predictors of rotational alignment in proximal tibial shaft fractures: a cadaveric study.

AIM: The treatment of tibial fractures with an intramedullary nail is an established procedure. However, torsional control remains challenging using intraoperatively diagnostic tools. Radiographic tools such as the Cortical Step Sign (CSS) and the Diameter Difference Sign (DDS) may serve as tools for diagnosing a relevant malrotation. The aim of this study was to investigate the effect of torsional malalignment on CSS and DDS parameters and to construct a prognostic model to detect malalignment. METHODS: A proximal tibial shaft fracture was set in human tibiae. Torsion was set stepwise from 0° to 30° in external and internal torsion. Images were obtained with a C-arm and transferred to a PC for measuring the medical cortical thickness (MCT), lateral cortical thickness (LCT), tibial diameter (TD) in AP and the anterior cortical thickness (ACT) as well as the posterior cortical thickness (PCT) and the transverse diameter (TD) of the proximal and the distal main fragment. RESULTS: There were significant differences between the various degrees of torsion for each of the absolute values of the examined variables. The parameters with the highest correlation were TD, LCT and ACT. A model combining ACT, LCT, PCT and TD lateral was most suitable model in identifying torsional malalignment. The best prediction of clinically relevant torsional malalignment, namely 15°, was obtained with the TD and the ACT. CONCLUSION: This study shows that the CSS and DDS are useful tools for the intraoperative detection of torsional malalignment in proximal tibial shaft fractures and should be used to prevent maltorsion.

Risk factors for aseptic loosening in complex revision total knee arthroplasty using rotating hinge implants.

PURPOSE: This study aimed to determine the risk factors of aseptic loosening (AL) in complex revision total knee arthroplasty (TKA) cases using rotating hinge knee prosthesis. METHODS: Patients who had undergone re-revision rotating hinge prosthesis surgery between January 2012 and December 2017 were included. Parameters related to AL were retrospectively reviewed. For this purpose, 31 aseptic loosening patients and 30 control patients were included in the study. Various risk factors were evaluated. Risk factors for AL after re-revision were determined using univariate and multiple logistic regression analyses. RESULTS: Thirty-one AL patients and 30 control patients were included. In the AL group, tibial tantalum cone and impaction grafting were performed significantly less frequently than the control group (p = 0.002 and p < 0.001). Logistic regression analysis revealed that smoking, right-sided TKA, and large femoral canal anteroposterior diameter were factors that increased the risk of AL after re-revision, while tibial tantalum cone decreased the risk of loosening. Smokers had an 11.847-fold higher risk for AL; right-sided TKA led to a 4.594-fold higher risk for AL. However, the presence of a tibial tantalum cone was associated with an 8.403-fold lower risk for AL. CONCLUSIONS: We conclude that smoking, right-sided prosthesis, and large femoral canal diameter increased the risk of AL, while tantalum cone and impaction grafting reduced this risk in patients who underwent re-revision surgery with rotating hinge prosthesis after TKA.

The 2018 International Consensus Meeting Minor Criteria for Chronic Hip and Knee Periprosthetic Joint Infection: Validation From a Single Center.

BACKGROUND: Recently, a revised definition of the minor criteria scoring system for diagnosing periprosthetic joint infection (PJI) was developed by the second International Consensus Meeting on musculoskeletal infection. The new system combines preoperative and intraoperative findings, reportedly achieving high sensitivity and specificity. We aimed to validate the modified scoring system at a high-volume center. METHODS: We retrospectively reviewed patients who underwent a revision total hip or knee arthroplasty at our institution from May 2015 to August 2018. Serum C-reactive protein, synovial white blood cell count and polymorphonuclear percentage, leukocyte esterase test, alpha-defensin, microbiological and histologic results, and documented existence of sinus tract and intraoperative purulence were available for all patients. Cases with at least 1 major criterion were considered as infected. Using the new minor criteria, a score of ≥6 reflects PJI, while a score <3 can be considered as noninfected. Sensitivity, specificity, mean accuracy (ACC), positive predictive value (PPV), and negative predictive value (NPV) were analyzed. RESULTS: A total of 345 cases were included. A cutoff score of ≥6 points had the following diagnostic performance: area under the curve (AUC) = 0.90; ACC = 0.88; sensitivity = 0.96; specificity = 0.84; PPV = 0.70; NPV = 0.98. Diagnostic performance was better for the hip (AUC = 0.92; ACC = 0.90; sensitivity = 0.96; specificity = 0.86; PPV = 0.81; NPV = 0.98) than the knee (AUC = 0.89; ACC = 0.85; sensitivity = 0.95; specificity = 0.83; PPV = 0.59; NPV = 0.98). CONCLUSION: The modified scoring system proposed by the 2018 International Consensus Meeting in diagnosing PJI showed high sensitivity and a good performance, especially as rule-out diagnostic criteria. The cutoff level seems to be different between the hip and knee. Further validation studies considering the acknowledged limitations are recommended.

Modified less invasive anterior subcutaneous fixator for unstable Tile-C-pelvic ring fractures: a biomechanical study.

BACKGROUND: Operative procedures for unstable pelvic ring fractures remain controversially discussed. Minimally invasive treatment options for pelvic ring fractures have several benefits for the patient. But they can also provide disadvantages. Anterior subcutaneous pelvic fixation (INFIX) has shown promising biomechanical results in pelvic ring fractures, but there is a high complication rate of nerve injuries. An additional screw to the INFIX seems to be more stable. The aim of this study is to compare biomechanical stability of a new modified unilateral INFIX fixing the unilateral injured pelvic ring with the standard INFIX. METHODS: 24 composite synthetic full pelvises were used in this study. 4 groups each with a number of six pelvic specimens were randomly assigned. A C1.3-type pelvic fracture was made with an osteotomy of the sacrum and an osteotomy of the anterior pelvic ring. Fracture fixation was performed within the four groups: (1) unilateral INFIX, (2) "extended" unilateral INFIX + additional pubic ramus pedicle screw, (3) bilateral INFIX, (4) "extended" bilateral INFIX + additional pubic ramus pedicle screw. All specimens were cyclic loaded with 200 N until maximum of 300 N. Distance/dislocation of the fracture fragments were detected with 3D-ultrasound measuring system. Stiffness was calculated. RESULTS: Extended unilateral INFIX showed the lowest mean dislocation. Lowest rotational stability was displayed by the standard bilateral INFIX. A significant difference (P = 0.04) was shown between the extended unilateral INFIX and the "standard" bilateral INFIX in terms of rotational stability. Extended unilateral INFIX showed significantly improved stability of anterior fracture dislocation (P = 0.01) and unilateral INFIX showed the highest rotational stiffness. Anterior fixation stiffness of the unilateral INFIX was significantly improved using an additional symphysis/pubic ramus screw (P = 0.002). CONCLUSION: Extended unilateral INFIX (+ additional pubic ramus pedicle screw) is a feasible minimally invasive treatment for anterior pelvic ring fractures. Higher stability and lower probability of bilateral nerve damage is provided by the extended unilateral INFIX compared to the standard bilateral INFIX.

Prognostic factors for long-term survival after adult liver transplantation.

PURPOSE: Prognostic factors for survival ≥ 15 years and life years lost after liver transplantation are largely unknown. METHODS: One thousand six hundred thirty primary adult liver transplants between 1983 and 2014 were analyzed. Risk factors for survival were identified with multivariable Cox regression and subsequently tested for their relevance as prognostic factors for observed 15-year survival using multivariable logistic regression and c statistics. The difference of life expectancy between a matched national reference population and survival in patients with post-transplant survival ≥ 15 years was calculated. RESULTS: Survival of ≥ 15 years was observed in 361 patients (22%). Sixty-nine adults died after more than 15 years losing a median of 15 years of life expectancy. One of those patients lived longer while 292 patients still have the chance to survive longer than their normal life expectancy. The indication primary sclerosing cholangitis (PSC) and later eras of transplantation were identified as significant independent protective factors while recipient age > 36.8 years, graft loss due to initial non-function or thrombosis, the indications hepatocellular carcinoma (HCC), hepatitis-C-virus-related cirrhosis (HCV-cirrhosis) and all other indications, donor age > 53 years, the number of surgical complications, and operative durations > 4.5 h were identified as significant independent risk factors limiting survival. All of these factors except the duration of operation had also a significant independent influence on observed 15-year survival (AUROC = 0.739). CONCLUSIONS: Recipients can exceptionally live longer than their normal life expectancy. Older recipients and patients with the indications HCC, HCV-cirrhosis, or other indications except PSC, should be transplanted with younger donor organs.

Outcome of subtrochanteric femur resection in patients with spinal cord injuries.

OBJECTIVE: To analyse the clinical outcome of subtrochanteric femur resection in patients with infected hip joints caused by pressure ulcers (PUs) in patients following spinal cord injury (SCI). METHOD: A retrospective cohort study, carried out between January 2004 and December 2015. Only patients receiving a subtrochanteric femur resection were included. SCI patients were treated for a hip joint infection caused by a PU. Primary outcome measures were to work out the revision rates and the rate of heterotopic ossification occurrence. RESULTS: At the time of admission, 37 out of the 56 participating patients (66.1%) showed a category IV PU with the ischium being most commonly affected (n=25, 44.6%). The subtrochanteric femur resection was combined either with a direct wound closure (n=29; 51.8%) or a myocutaneous flap (n=27; 48.2%). The mean number of surgeries was 2.6 (1-4; SD=1.6) and 21 patients were successfully treated by a single surgery. Of the patients, 28 had wound healing disorders (50%) and required a revision surgery, and 24 (42.9%) developed a postoperative heterotopic ossification. CONCLUSION: Hip joint infection caused by PUs can be treated with subtrochanteric femur resection. However, the number of postoperative complications is still high

High bacterial contamination rate of electrocautery tips during total hip and knee arthroplasty.

PURPOSE: The aim of the study was to quantify the bacterial contamination rate of electrocautery tips during primary total joint replacement (TJR), as well as during aseptic and septic revision TJR. METHODS: A total of 150 electrocautery tips were collected between April and July 2017. TJR surgeries were divided into three groups: (1) primary, (2) aseptic and (3) septic revisions. In each group, a total of 50 electrocautery tips were collected. A monopolar electrocautery with a reusable stainless-steel blade tip was used in all cases. The rate of bacterial contamination was determined for all groups. Correlation of exposure time and type of surgery was analyzed. RESULTS: The overall bacterial contamination rate was 14.7% (95% CI 9.4 to 21.4%). The highest contamination rate occurred in the septic revision group (30.0%; 95% CI 17.9 to 44.6%), followed by the primary cases group (10.0%; 95% CI 3.3 to 21.8%) and the aseptic revision group (4.0%; 95% CI 0.5 to 13.7%). Exposure time did not affect the bacterial contamination rate. In 12 out of 15 (80%) contaminations identified in the septic group, we found the same causative microorganism of the prosthetic joint infection on the electrocautery tip. CONCLUSIONS: The bacterial contamination of the electrocautery tips is relatively high, especially during septic hip revision arthroplasty. Electrocautery tips should be changed after debridement of infected tissue.

Preliminary results of a novel spacer technique in the management of septic revision hip arthroplasty.

INTRODUCTION: Mechanical failure due to dislocation, fracture and acetabular wear is a major complication associated with the use of spacers in the management of periprosthetic joint infection (PJI). We have developed a novel custom-made spacer in the setting of two-stage septic revision hip arthroplasty and present the preliminary results of our technique. MATERIALS AND METHODS: Between May 2015 and November 2017, 30 patients underwent hip revision using the ENDO spacer technique in the setting of a two-stage septic exchange arthroplasty. The technique involves the dual mobility liner and the downsized stainless cemented straight stem in combination with antibiotic-loaded PMMA bone cement. The primary outcome measure was the overall spacer complication rate, particularly spacer dislocation. Furthermore, functional outcome using the Harris Hip Score (HHS) before spacer implantation and prior re-implantation was evaluated. RESULTS: The mean age of the patients was 69.8 years (range from 45 to 85; SD = 9.9 years). No microorganisms were preoperatively found in 23 (76.7%) cases. Successful re-implantation was performed in all patients after a mean spacer duration time of 53.6 days (range 14-288 days; SD = 48.2). Spacer-related complications occurred in only two patients (6.7%). The HHS significantly improved from 34.0 (range 3-62; SD = 15.1) to 48.1 (range 11-73; SD = 15.7) (p = 0.0008). CONCLUSIONS: The ENDO spacer surgical technique is a feasible option in the treatment of periprosthetic joint infection (PJI), with a low dislocation rate. Furthermore, it allows early mobilization with the possibility of full-weight bearing.

The effect of distal tibial rotation during high tibial osteotomy on the contact pressures in the knee and ankle joints.

PURPOSE: Intraoperative fracture of the lateral cortex fractures of the tibia is a potential complication of high tibial osteotomy (HTO), which may result in inadequate rotational alignment of the distal tibia. Our aim was to determine how rotational malalignment of the distal tibial segment distal would affect intraarticular contact pressure distribution in the knee and ankle joints. METHODS: A medial, L-shaped opening-wedge HTO was performed on seven human lower body specimens. A stainless steel device with integrated load cell was used to axially load the leg. Pressure-sensitive sensors were used to measure intraarticular contact pressures. Intraoperative changes in alignment were monitored in real time using computer navigation. Measurements were performed in the native knee alignment, after 10° and 15° of alignment correction and with the distal tibia fixed at 15° of external rotation. RESULTS: Moderate-to-large alignment changes after medial opening-wedge HTO resulted in a shift in intraarticular contact pressures from the medial compartment of the knee towards the lateral compartment. However, fixation of the distal tibial segment at 15° of external rotation neutralized this intended beneficial effect. In the ankle, external rotation of the distal tibia also caused a reduction in contact pressures and tibiotalar contact area. CONCLUSION: Malrotation of the distal tibial fragment negates the intended effect of offloading the diseased compartment of the knee, with the contact pressures remaining similar to those of the native knee. Furthermore, malrotation leads to abnormal ankle contact pressures. Care should be taken to ensure appropriate rotational alignment of the distal tibial segment during intraoperative fixation of HTO procedures.

Sectioning the anterolateral ligament did not increase tibiofemoral translation or rotation in an ACL-deficient cadaveric model.

PURPOSE: The anterolateral ligament (ALL) has been proposed as a possible extra-articular stabiliser of the knee. Injury to the ALL may result in residual instability following surgical reconstruction of a ruptured anterior cruciate ligament (ACL). Few studies have evaluated the biomechanical role of the ALL. The purpose of this study was to investigate whether sectioning the ALL would have an influence on tibiofemoral translation or rotation during the anterior drawer, Lachman, pivot shift, external rotation, and internal rotation tests in an ACL-deficient knee. METHODS: Only whole-body specimens having an ALL were included in this study. Lachman, anterior drawer, external rotation, and internal rotation tests were performed manually. Pivot shift test was done using a mechanised pivot shifter. The amount of tibiofemoral translation and rotation was recorded by a navigation system. Each specimen was tested in its native state, after sectioning the ACL, and after combined sectioning of the ACL and the ALL. RESULTS: In six out of 14 cadaveric knees, an ALL could be identified. The ACL-deficient knee had significantly more tibiofemoral translation and rotation compared to the native knee (P < 0.05). However, no changes in the magnitudes of translation or rotation were seen after subsequent sectioning of the ALL compared to the ACL-deficient knee (P > 0.05). CONCLUSION: Adding an ALL lesion in an ACL-deficient knee did not increase tibiofemoral instability in this cadaveric model. It remains unclear whether injury to the ALL would result in substantial knee instability in the setting of ACL injury in vivo. Further research is warranted to fully elucidate the role of the ALL during knee kinematics and to determine in which scenarios ALL repair would be warranted. Understanding the function of the ALL may improve the current treatment strategies for ACL ruptures.

Midterm results after unicompartmental knee replacement with all-polyethylene tibial component: a single surgeon experience.

PURPOSE: The aim of this study was to determine the survival rate, the causes of failure, and the functional outcomes of an all-polyethylene tibial unicompartmental knee prosthesis. METHODS: One hundred (100) nonselected, consecutive patients indicated for unicompartmental knee replacement for isolated medial knee compartment osteoarthritis by a single surgeon at a single institution from 2000 to 2004 were included in this study. Data was collected retrospectively at final follow-up from the hospital electronic database, including progress notes, demographic information, Hospital for Special Surgery (HSS) Knee Score, details on the surgical procedure, reoperations/revisions, and mortality. A survival analysis was performed to estimate the probability of survival over time. RESULTS: The survival probability of the all-polyethylene UKA implant was 95.4 % after a mean follow-up of 8 years, which is comparable to reports from studies using metal-backed modular designs for UKA. The causes of failure were progression of arthritis in adjacent compartments (2 %) and loosening of the tibial component (2 %). The mean preoperative HSS knee score improved from 36.6 ± 14.3 to 76.6 ± 21.6 at latest follow-up (p < 0.0001). CONCLUSIONS: In summary, an all-polyethylene tibial component has equivalent survivorship to modular designs. Implant selection does not seem to have great influence on the outcome, but rather the success depends on appropriate indications and surgical technique.

Preoperative virtual reduction reduces femoral malrotation in the treatment of bilateral femoral shaft fractures.

INTRODUCTION: In bilateral femoral shaft fractures, significant malrotation (>15°) occurs in about 40 % of cases after intramedullary nailing. Most of the methods that provide rotational control during surgery are based on a comparison to the intact femur and, thus, not applicable for bilateral fractures. In this study, we evaluated if preoperative virtual reduction can help improving rotational alignment in patients with bilateral femoral shaft fractures. MATERIALS AND METHODS: Seven patients with bilateral femoral shaft fractures were initially treated with external fixation of both femurs. After obtaining a CT scan of both legs, the fractures were reduced virtually using the software program VoXim®, and the amount and direction of rotational correction were calculated. Subsequently, the patients were treated by antegrade femoral nailing and rotation was corrected to the preoperatively calculated amount. RESULTS: After external fixation, the mean rotational difference between both legs was 15.0° ± 10.2°. Four out of seven patients had a significant malrotation over 15°. Following virtual reduction, the mean rotational difference between both legs was 2.1° ± 1.2°. After intramedullary nailing, no case of malrotation occurred and the mean rotational difference was 6.1° ± 2.8°. CONCLUSIONS: Preoperative virtual reduction allows determining the pretraumatic femoral antetorsion and provided useful information for the definitive treatment of bilateral femoral shaft fractures. We believe that this procedure is worth being implemented in the clinical workflow to avoid malrotation after intramedullary nailing.

A cadaver study comparing intraoperative methods to analyze lower limb alignment.

BACKGROUND: Conventional intraoperative determination of lower limb alignment is essential for orthopedic surgical treatment. Current methods include the cable, alignment rod, and axis board methods. QUESTION/PURPOSES: Are there differences in accuracy and reliability? What are the individual differences in applicability and radiation exposure? METHODS: Twenty legs from 12 fresh-frozen cadavers were randomly selected. After fixation of the legs, measurements were performed using the cable, alignment rod, and axis board methods. Afterwards, all cadavers were subjected to CT scanning. Intersection of the mechanical leg axis with the tibia plateau was calculated as the percentage of the tibia plateau, beginning at the medial border (0%) and ending at the lateral border (100%). Results are presented as mean ± standard deviation (SD). RESULTS: Compared with CT measurements, differences of the intersection at the tibia plateau were 3.9 ± 8.5% with the cable method, 3.6 ± 7.6% using the alignment rod, and 3.6 ± 9.6% using the axis board. The difference among all measurements was not statistically significant (p = 0.450). The average intersection of the mechanical axis was 43.95 ± 5.15% using the cable method, 43.93 ± 5.49% using the alignment rod, and 43.77 ± 5.92% using the axis board. CT measurements revealed an average intersection of 42.46 ± 5.22%. There was no statistically significant difference among conventional results (p = 0.976). We demonstrated good intraobserver reliability for all three methods (cable method, ICC = 0.97; alignment rod, ICC = 0.95; and axis board, ICC = 0.96). There were no statistically significant differences regarding radiation time (p = 0.349) or dose area product (p = 0.823). CONCLUSIONS: All described measurements demonstrated valid measurement of lower limb alignment. With minimal effort, all three methods present a practical and uncomplicated way to control the mechanical axis.

Laser method for intraoperative evaluation of lower extremity alignment: comparison of a novel technique to CT and a conventional method.

INTRODUCTION: Accurate restoration of mechanical alignment is an important factor in reconstructive surgery of the lower extremity. Conventional intraoperative methods, such as using an electrocautery cable, provide only a momentary evaluation of alignment. In this study, we evaluated a novel technique using a laser emitter, which projected the mechanical axis of the lower extremity, providing continuous intraoperative information on alignment. MATERIALS AND METHODS: Alignment of 16 cadaver lower extremities was measured using the electrocautery cable method, the laser method, and CT scan as the standard measurement. The mechanical axis was defined by a line from the center of the femoral head to the center of the ankle. For simplifying measurements the intersection with the tibial plateau was divided into percentages from the medial border (0 %) to the lateral border (100 %). For using the laser method a laser emitting and laser catching device was developed, which is positioned and centered on the femoral head and the ankle using an image intensifier. By catching the laser on the knee region the actual mechanical axis is marked. RESULTS: The data demonstrated good correlation of the laser method when compared to the cable method (P = 0.44). Comparison of the average mechanical axis between cable method and CT (P = 0.819) and laser method and CT (P = 0.647) did not show a statistically significant difference. Average radiation time in comparison between cable method and laser method showed a statistically significant difference (P = 0.013), with the laser method requiring more radiation time. CONCLUSION: Determination of the mechanical axis during surgery remains a difficult clinical problem. Restoration of alignment is an important prognostic factor for surgical outcome. Based on these data, the laser method represents a simple, yet effective tool for continuous intraoperative evaluation of lower extremity alignment.

The physiological range of femoral antetorsion.

INTRODUCTION: Intramedullary nailing is a common method for fixation of femoral diaphyseal shaft fractures. However, postoperative malrotation does occur in 20-30 % of patients, as intraoperative assessment of antetorsion remains difficult. The estimated average antetorsion angle is 15°. However, it is not clear whether antetorsion correlates with individual characteristics such as age, gender, or femoral length. This information may help surgeons to better estimate the correct target rotation before and during surgery. MATERIALS AND METHODS: The antetorsion of 211 healthy femurs was measured using torsion difference CTs according to the technique published by Jend. Correlations with age, gender, and femoral length were calculated. RESULTS: A significant negative correlation of age and antetorsion was found for women aged 0-20. Older women and men did not show any correlation between antetorsion and age. There was no correlation between antetorsion and femoral length. Mean values differed between 17.8° ± 8.9° and 22.7° ± 10.7° in women and 15.3° ± 8.0° and 21.4° ± 9.7° in men. CONCLUSIONS: Antetorsion is mostly independent of body height and age, the latter except in women younger than 20. The so-far-estimated physiologic antetorsion of about 15° seems to be a little higher in most people.

Variability in knee laxity in anterior cruciate ligament deficiency using a mechanized model.

PURPOSE: To establish normative values for the magnitude of anterior tibial translation (ATT) in the Lachman and pivot shift tests in the intact and anterior cruciate ligament (ACL)-deficient states, and to explore whether a correlation in ATT magnitude exists between the Lachman and pivot shift tests. METHODS: Twenty-six fresh frozen cadaveric hip-to-toe specimens were used. Mechanized testing was performed to simulate both a Lachman and pivot shift test with the ACL intact. Tests were repeated after sectioning the ACL. ATT was recorded using a computer navigation system. Difference in ATT after sectioning was calculated for each specimen. RESULTS: For the Lachman, mean lateral compartment ATT in the intact knee was 5.3 mm (SD = 2.8 mm). After sectioning the ACL, translation increased to 11.4 mm (SD = 3.9 mm; P < 0.05). For the mechanized pivot shift, mean lateral compartment ATT in the intact knee was -0.2 mm (SD = 2.6 mm). After sectioning the ACL, translation increased to 8.2 mm (SD = 3.1 mm; P < 0.05). No correlation in the magnitude of ATT was found between the intact and ACL-deficient knees for either the Lachman or pivot shift tests, or between both tests (Cronbach's α < 0.7). CONCLUSIONS: No correlation was found between the Lachman and pivot shift test in both the intact and ACL-deficient knee. This suggests that the Lachman cannot be used as a surrogate for the pivot shift as the magnitude of the Lachman did not predict the magnitude of the pivot shift.