[Value of radiographic examination of the knee joint for the orthopedic surgeon]

The ultrastructural and morphological characteristics of the anterior cruciate ligament of the pig: a study using 7.0-Tesla diffusion tensor imaging

OBJECTIVE

Diffusion tensor imaging research on the anterior cruciate ligament (ACL) is limited, and no study has revealed the ACL fibrous microstructure by 7.0-Tesla magnetic resonance imaging. Therefore, we used magnetic resonance imaging to assess the ACL.

METHODS

Eight porcine ACLs were investigated by diffusion tensor imaging. Imaging was performed with a 7.0-Tesla scanner using a diffusion-weighted two-dimensional spin-echo echo-planar imaging pulse sequence optimised for muscle. The diffusion tensor eigenparameters, fractional anisotropy (FA), and apparent diffusion coefficient (ADC) were used for bones and muscles. Three-dimensional projection maps of the principal eigenvectors were plotted to visualise the microstructure.

RESULTS

The mean FA and ADC for the ACL were 0.27 ± 0.079 and 0.0012 ± 0.0005, respectively. There were no significant differences between the values in the proximal and distal portions . However, the ADC was smaller in the centre than on the sides (0.0015 ± 0.0007), and the mean FA was larger in the centre than on the sides (0.42 ± 0.23). The ACL fibres were parallel on the proximal and distal sides but interweaved in the centre.

CONCLUSIONS

These findings may be beneficial for artificial ligaments.

The Rosenberg view and coronal stress radiographs give similar measurements of articular cartilage height in knees with osteoarthritis

PURPOSE

Choosing the optimal radiographic methods to diagnose the cartilage height and degree of knee osteoarthritis is crucial to determine suitability for unicompartmental knee replacement. This study aims to evaluate and compare articular cartilage thickness measured using the Rosenberg view and coronal stress radiography. Intra- and interrater agreement and test-retest reliability of each method were determined. The hypothesis of the study was that the Rosenberg view and coronal stress radiographs provide similar assessments of articular cartilage height in the medial and lateral knee compartments of osteoarthritic knees.

METHODS

A prospective diagnostic study, including 73 patients was performed. Inclusion criteria were enrollment for either a medial unicompartmental or a total knee replacement. Radiographs were taken as the Rosenberg view, and coronal stress radiography using the Telos stress device. Repeated measurements were performed. Experienced knee surgeons performed measurements of cartilage height at a standardized location of joint space width (JSW), and a rater-perceived location of minimal joint space width (mJSW), thus allowing for reliability and agreement analysesusing weighted kappa. Coronal stress measurements were ultimately compared to the Rosenberg view using Spearman's rank correlation.

RESULTS

A total of 12,264 measurements were performed. The radiographic methods proved substantial reliability. Intra- and interrater agreement showed substantial to almost perfect agreement. A very strong correlation was observed in the medial knee compartment (r = 0.91; CI = 0.84-0.95; p < 0.001), with a mean difference of 0.1 mm and limits of agreement of - 1.5 to 1.7 mm, when comparing JSW between the Rosenberg view and varus stress. Only a strong correlation was observed medially when using mJSW, and when using this measurementmore incidences of bone-on-bone were observed than when measuring with JSW. A Strong correlation was observed in the lateral knee compartment (r = 0.83; CI = 0.71-0.89; p < 0.001), with a mean difference of 0.62 mm and limits of agreement of - 1.5 to 2.7 mm, when comparing JSW between the Rosenberg view and valgus stress.

CONCLUSION

The Rosenberg view is similar to 20° coronal valgus-varus stress radiography for determining articular cartilage thickness. Both techniques can be used in a clinical setting. Therefore, extra radiographs, equipment and expertise could be saved, when solely utilizing the Rosenberg view which is simple to perform.

LEVEL OF EVIDENCE

III.

Does MIPO of fractures of the distal femur result in more rotational malalignment than ORIF? A retrospective study

PURPOSE

Intraoperative control of rotational malalignment poses a big challenge for surgeons when using modern MIPO (minimally invasive plate osteosynthesis) techniques. We hypothesized that distal femoral fractures treated with MIPO technique are more often fixed in malrotation than those treated with open reduction internal fixation (ORIF).

METHODS

In this retrospective study, we identified 20 patients who met the inclusion criteria and agreed to take part in the study. In ten patients MIPO was applied, in the other ten ORIF was used. Mean age was 44.8 (19-71 years). Functional status was assessed using clinical scores (Harris Hip Score, WOMAC Hip, KS Score, WOMAC Knee, Kujala Score). Rotational alignment was assessed with magnetic resonance imaging and compared to the opposite leg.

RESULTS

We discovered a significant difference in the mean rotational difference between the MIPO group (14.3°) and the ORIF group (5.2°). Functionally, patients in the ORIF group outperformed patients in the MIPO group in all clinical scoring systems although no one proved to be statistically significant. MIPO technique was associated with significantly more rotational malalignment compared to ORIF in distal femur fracture fixation. However, implant failure and nonunion was more common in the ORIF group, with a revision rate of 3 versus 1 in the ORIF group. Clinical scoring did not significantly different between both groups.

CONCLUSION

Taking into account the undisputable advantages of minimally invasive surgery, improved teaching of methods to avoid malrotation as well as regular postoperative investigations to detect any malrotation should be advocated.

Small improvements in mechanical axis alignment achieved with MRI versus CT-based patient-specific instruments in TKA: a randomized clinical trial

BACKGROUND

Patient-specific instrumentation in TKA has the proposed benefits of improving coronal and sagittal alignment and rotation of the components. In contrast, the literature is inconsistent if the use of patient-specific instrumentation improves alignment in comparison to conventional instrumentation. Depending on the manufacturer, patient-specific instrumentation is based on either MRI or CT scans. However, it is unknown whether one patient-specific instrumentation approach is more accurate than the other and if there is a potential benefit in terms of reduction of duration of surgery.

QUESTIONS/PURPOSES

We compared the accuracy of MRI- and CT-based patient-specific instrumentation with conventional instrumentation and with each other in TKAs. The three approaches also were compared with respect to validated outcomes scores and duration of surgery.

METHODS

A randomized clinical trial was conducted in which 90 patients were enrolled and divided into three groups: CT-based, MRI-based patient-specific instrumentation, and conventional instrumentation. The groups were not different regarding age, male/female sex distribution, and BMI. In all groups, coronal and sagittal alignments were measured on postoperative standing long-leg and lateral radiographs. Component rotation was measured on CT scans. Clinical outcomes (Knee Society and WOMAC scores) were evaluated preoperatively and at a mean of 3 months postoperatively and the duration of surgery was analyzed for each patient. MRI- and CT-based patient-specific instrumentation groups were first compared with conventional instrumentation, the patient-specific instrumentation groups were compared with each other, and all three approaches were compared for clinical outcome measures and duration of surgery.

RESULTS

Compared with conventional instrumentation MRI- and CT-based patient-specific instrumentation showed higher accuracy regarding the coronal limb axis (MRI versus conventional, 1.0° [range, 0°-4°] versus 4.5° [range, 0°-8°], p < 0.001; CT versus conventional, 3.0° [range, 0°-5°] versus 4.5° [range, 0°-8°], p = 0.02), femoral rotation (MRI versus conventional, 1.0° [range, 0°-2°] versus 4.0° [range, 1°-7°], p < 0.001; CT versus conventional, 1.0° [range, 0°-2°] versus 4.0° [range, 1°-7°], p < 0.001), and tibial slope (MRI versus conventional, 1.0° [range, 0°-2°] versus 3.5° [range, 1°-7°], p < 0.001; CT versus conventional, 1.0° [range, 0°-2°] versus 3.5° [range, 1°-7°], p < 0.001), but the differences were small. Furthermore, MRI-based patient-specific instrumentation showed a smaller deviation in the postoperative coronal mechanical limb axis compared with CT-based patient-specific instrumentation (MRI versus CT, 1.0° [range, 0°-4°] versus 3.0° [range, 0°-5°], p = 0.03), while there was no difference in femoral rotation or tibial slope. Although there was a significant reduction of the duration of surgery in both patient-specific instrumentation groups in comparison to conventional instrumentation (MRI versus conventional, 58 minutes [range, 53-67 minutes] versus 76 minutes [range, 57-83 minutes], p < 0.001; CT versus conventional, 63 minutes [range, 59-69 minutes] versus 76 minutes [range, 57-83 minutes], p < .001), there were no differences in the postoperative Knee Society pain and function and WOMAC scores among the groups.

CONCLUSIONS

Although this study supports that patient-specific instrumentation increased accuracy compared with conventional instrumentation and that MRI-based patient-specific instrumentation is more accurate compared with CT-based patient-specific instrumentation regarding coronal mechanical limb axis, differences are only subtle and of questionable clinical relevance. Because there are no differences in the long-term clinical outcome or survivorship yet available, the widespread use of this technique cannot be recommended.

Intramedullary control of distal femoral resection results in precise coronal alignment in TKA

INTRODUCTION

There is still a relevant rate of outliers in coronal alignment >3° when the conventional technique is used, potentially accompanied by a poorer long-term clinical outcome and a reduced longevity of the implant. Intraoperative implementation of preoperative planning and above all checking of the bone resections carried out are decisive for reinstating a straight leg axis. Intramedullary control of femoral resection has not been described to date. The objective of this study was to present a new technique for the intramedullary control of femoral resection and the results obtained using this method.

METHODS

All patients who underwent primary total knee arthroplasty with the new intramedullary control of femoral resection were included in this retrospective study. The frequency of the need for correction of the saw cuts was documented. The radiological assessment included pre- and postoperative whole-leg standing radiographs. In the process, the whole-leg axis, AMA, entry point, LDFA and MPTA were evaluated preoperatively. On the postoperative radiographs, the whole-leg axis and the alignment of the femoral and tibial components were evaluated.

RESULTS

One hundred and sixty-two total knee arthroplasties (TKAs) were included in the study. The average age was 68.7 years. The preoperative malalignment was on the average 8.2° ± 4.7° (23.8° varus to 17.3° valgus). The postoperative whole-leg axis was on the average 1.3° ± 1.1° (5.5° varus to 4.3° valgus). The femoral component showed a deviation from the mechanical axis of 0.1° ± 1.2° (4.3° varus to 3.7° valgus) and the tibial component a deviation from the mechanical tibial axis of 0.3° ± 1.2° (4.2° varus to 2.5° valgus).

CONCLUSIONS

The new technique of intramedullary control of distal femoral resection, together with preoperative planning, leads to a precise alignment of the femoral component in the coronal plane. Thus, for the first time, a simple and effective tool for checking distal femoral resection is available for standardized use.

Comparison of positions of the trochlear groove line and the vertical midline of the pericondylar rectangle on axial computed tomography: a retrospective pilot study

OBJECTIVE

To compare the positions of the trochlear groove (TG) line and the vertical midline of the pericondylar rectangle on axial computed tomography (CT).

MATERIALS AND METHODS

A retrospective pilot study was conducted in February and March 2011 comprising 14 knees in 9 consecutive patients with patellofemoral pain, a normal trochlear angle (124°-145°), and no medical record of prior knee surgery. After the axial CT image displaying the center of the trochlear groove ("reference cut") with a normal trochlear angle was identified, the pericondylar rectangle was drawn and located in the first quadrant of the Cartesian rectangular coordinate system. The x-coordinates of the vertical lines passing through the most posterior point of the trochlear groove (TG line) and the midpoints of the horizontal sides of the pericondylar rectangle (vertical midline) were obtained at 2-week intervals and statistically analyzed as matched pairs for differences (Wilcoxon signed rank test), agreements (Bland-Altman plot, intraclass correlation coefficient [ICC]) and relative variations (coefficient of variation [CV]).

RESULTS

There were no statistically significant differences between matched pairs (2-tailed p from 0.583 to 0.641) whereas the agreements were substantial (bias = -0.37 and -0.45 respectively, ICC = 0.688 and 0.670 respectively) to almost perfect for duplicate measurements (bias = 0.11 and 0.04 respectively, ICC = 0.975 and 0.998 respectively), with much less relative variation with regard to the vertical midline (CV = 1.22% to CV = 0.34% respectively).

CONCLUSION

The positions of the TG line and the vertical midline of the pericondylar rectangle on axial CT were identical. The latter was identified regardless of trochlear morphology.

The painful knee after TKA: a diagnostic algorithm for failure analysis

Pain after total knee arthroplasty (TKA) represents a common observation in about 20% of the patients after surgery. Some of these painful knees require early revision surgery within 5 years. Obvious causes of failure might be identified with clinical examinations and standard radiographs only, whereas the unexplained painful TKA still remains a challenge for the surgeon. It is generally accepted that a clear understanding of the failure mechanism in each case is required prior considering revision surgery. A practical 10-step diagnostic algorithm is described for failure analysis in more detail. The evaluation of a painful TKA includes an extended history, analysis of the type of pain, psychological exploration, thorough clinical examination including spine, hip and ankle, laboratory tests, joint aspiration and test infiltration, radiographic analysis and special imaging techniques. It is also important to enquire about the length and type of conservative therapy. Using this diagnostic algorithm, a sufficient failure analysis is possible in almost all patients with painful TKA.

[Imaging examinations of the patellofemoral joint]

Lesions in the patellofemoral region can be caused by trauma, chronic overloading, and especially regarding cartilage alterations by normal aging or pathologic processes. Very commonly these lesions lead to early arthrosis. An accurate clinical evaluation in all these patients is recommended. The combination of clinical information and radiological examinations should end up with an exact diagnosis.As part of the radiological evaluation of complaints of the patellofemoral region MR imaging is of special value since this method allows direct visualization of all intra- and extra-articular structures and their alterations, ultimately aiding in planning sufficient therapy. Moreover, is it possible to exclude pathology by MR imaging, which helps to prevent useless treatment and surgical procedures.

[Conventional navigation without computer and the lateral minimally invasive approach for contract valgus knee]

Valgus arthritic knees can basically be operated on by either a standard medial or a specific lateral approach. The classic lateral approach according to Keblish has some advantages, but also some disadvantages, relative to the standard medial parapatellar approach. A less invasive lateral approach means that osteotomy of tibia tubercle and eversion of the patella is no longer necessary. In view of our positive experiences with the minimally invasive surgical technique used for implantation of the lateral unicondylar prosthesis and for total knee arthroplasty in the case of varus knees, we have developed a minimally invasive lateral technique for use in valgus knees. The approach is a modification of the classic lateral approach used by Keblish. The procedure involves a lateral mini-arthrotomy with no need for osteotomy of the tubercle or eversion of the patella, and the surgery takes place step by step from a lateral approach. Modified cutting standard instruments are used. All operations have been carried out using "conventional navigation" without computers. This consists in preoperative planning based on radiographs of the whole leg, intraoperative controls before and after bone cuts, planning of the rotational positioning of the femur and tibia and postoperative checks of the alignment on standing radiographs of the whole leg. Preliminary results observed in the first 63 consecutive patients (average age 45-85 years) with contract valgus deformity [average 12 degrees valgus (6-19 degrees )] are very promising. Since 2004 we have used minimally invasive medial and lateral mini-midvastus approaches routinely for nearly all our primary total knee arthroplasties.

Von der tibiofemoralen Instabilität zur Luxation in der Knieendoprothetik

Tibiofemoral instability is increasingly recognized as a mode of failure in total knee arthroplasty (TKA). Severe instability may lead to dislocation. Wrong surgical technique and wrong choice of constraint of the prostheses are the main causes for instability. Malalignment, malrotation and intraoperatively uncorrected instability especially in flexion may lead to an unstable total knee arthroplasty. Cruciate-retaining designs and mobile platforms can be considered only in the presence of well-balanced ligaments. Cruciate-substituting designs give more stability and many people find them more forgiving. However, correction of varus-valgus instability and severe flexion laxity cannot be provided. Varus-valgus contrained designs cannot compensate for the absence of medial and lateral collateral ligaments. Such cases are most reliably treated with a linked implant (rotating hinge). The exact analysis of the cause of an unstable or dislocated total knee arthroplasty represents the most essential basis of a successful treatment. Exchange of the prostheses represents the most successful procedure. Correction of implantation failures should be performed. A more constrained design should be used if insufficient ligaments are found. Post-traumatic instability or dislocation represents an exception.

[Conventional X-rays and conventional tomography in orthopaedics. Current status]

Although sonography, computed tomography (CT) and magnetic resonance imaging (MRI) are common tools in radiology, conventional X-rays still have a place in orthopaedic diagnostic investigation. The advantages of radiographic imaging are high local resolution concerning bone, economy of time besides relatively low costs and worldwide experience. The conventional X-ray is indispensable for planning surgical procedures and clinical monitoring. For several pathological processes an X-ray is sufficient for diagnosis and therapy (i.e. degeneration, fracture). Early changes of the bone (i.e. osteonecrosis) cannot be detected by X-ray. CT and MRI have closed the diagnostic gap. Indications for conventional tomography are rare.