Michael T. Hirschmann

Increased in vivo patellofemoral loading after total knee arthroplasty in resurfaced patellae

PurposeThe primary purpose of the study was to investigate if and how patellar bone tracer uptake (BTU) distribution in SPECT/CT is influenced by patellar resurfacing and the position of femoral and tibial TKA component position.MethodsA total of 104 knees of 103 consecutive patients who underwent primary TKA were prospectively investigated. Primary patellar resurfacing was done in 40 knees while 64 had a TKA without patellar resurfacing. All patients underwent clinical assessment using the knee society score (KSS) and standardized radiographs and Tc-99m-HDP-SPECT/CT before and 12 and 24 months after TKA. Measurements of BTU including intensity and anatomical distribution pattern in eight different patellar regions were performed. Tibial and femoral TKA component position was assessed from 3D reconstructed CT data. Patellar height, thickness and tilt were measured and the distance between the tibial tuberosity and the trochlear groove (TT–TG) was measured. Univariate analysis was performed to identify differences between the two groups (p < 0.05).ResultsSignificantly higher BTU was found in the anterior, non-articular, areas of the patella in patients who underwent patellar resurfacing (p < 0.05). The BTU pattern was similar between the groups, as the maximal uptake in both groups was seen in the superior posterior parts and the minimal uptake was seen in the inferior anterior parts. The mean postoperative KSS was significantly higher in the unresurfaced group after 12 months (p < 0.05), but with no significant difference after 24 months.ConclusionsBased on the findings of the present study, patellar resurfacing is related to significantly higher BTU in the anterior parts of the patella and lower clinical outcomes. In light of these results, routine patellar resurfacing as part of a primary TKA might be reevaluated. SPECT/CT enables a precise localization of the BTU and might be considered as the ideal imaging modality for evaluation and investigate of patellofemoral disorders after TKA

Influence of surgical approach on heterotopic ossification after total hip arthroplasty – is minimal invasive better? A case control study

BackgroundHeterotopic ossification (HO) is a well-known complication after total hip arthroplasty (THA).Recently, the trend is to operate THA minimally invasive being less traumatic than standard approaches and promising a faster return to activity. The purpose of the study was to investigate if minimal invasive surgery (MIS), leads also to less HO after THA.MethodsThis retrospective study included 134 consecutive patients undergoing THA. In 42 (31.3%) patients a standard modified anterolateral (STD-Watson-Jones), in 28 (20.9%) patients a standard transgluteal Bauer approach (STD-Bauer), in 39 (29.1%) a MIS direct anterior approach (AMIS) and in 25 (18.7%) patients a MIS anterolateral (MIS-AL) approach was used. Standard preoperative anterior-posterior and lateral radiographs were assessed for occurrence of HO. HO was classified according to Brooker. In addition, short- and long-term adverse events were noted. Data was statistically analyzed using Chi-square tests, analysis of variance, multivariate data analysis and Pearson’s correlation (p < 0.05).ResultsOverall, HO was found in 38 caucasian patients (28.4%) after THA. The STD-Watson-Jones group showed the highest HO rate (45.2% n = 19) with a significant difference to the AMIS (23.1% n = 9) and STD-Bauer approach (14.3% n = 4). No statistical difference was found to the MIS-AL approach (24.0% n = 6). Postoperative complications did not differ significantly except for a higher incidence of Trendelenburg`s sign in STD-Bauer.ConclusionsThe rate and degree of HO after THA were significantly different with regards to the surgical approach. The standard modified anterolateral approach resulted in the highest HO rate, however, MIS approaches showed higher HO rates than the STD-Bauer.

Evaluation of patients with painful total hip arthroplasty using combined single photon emission tomography and conventional computerized tomography (SPECT/CT) – a comparison of semi-quantitative versus 3D volumetric quantitative measurements

BackgroundIt was the primary purpose of our study to evaluate the inter- and intra-observer reliability of a standardized SPECT/CT algorithm for evaluating patients with painful primary total hip arthroplasty (THA). The secondary purpose was a comparison of semi-quantitative and 3D volumetric quantification method for assessment of bone tracer uptake (BTU) in those patients.MethodsA novel SPECT/CT localization scheme consisting of 14 femoral and 4 acetabular regions on standardized axial and coronal slices was introduced and evaluated in terms of inter- and intra-observer reliability in 37 consecutive patients with hip pain after THA. BTU for each anatomical region was assessed semi-quantitatively using a color-coded Likert type scale (0-10) and volumetrically quantified using a validated software. Two observers interpreted the SPECT/CT findings in all patients two times with six weeks interval between interpretations in random order. Semi-quantitative and quantitative measurements were compared in terms of reliability. In addition, the values were correlated using Pearson`s correlation. A factorial cluster analysis of BTU was performed to identify clinically relevant regions, which should be grouped and analysed together.ResultsThe localization scheme showed high inter- and intra-observer reliabilities for all femoral and acetabular regions independent of the measurement method used (semiquantitative versus 3D volumetric quantitative measurements). A high to moderate correlation between both measurement methods was shown for the distal femur, the proximal femur and the acetabular cup. The factorial cluster analysis showed that the anatomical regions might be summarized into three distinct anatomical regions. These were the proximal femur, the distal femur and the acetabular cup region.ConclusionsThe SPECT/CT algorithm for assessment of patients with pain after THA is highly reliable independent from the measurement method used. Three clinically relevant anatomical regions (proximal femoral, distal femoral, acetabular) were identified.

Combined Meniscus and Cartilage Lesions

The intimate connections between the menisci and the osteochondral unit of the femoro-tibial compartment are based on their specific anatomical structure. Understanding the underlying structural and anatomical basis helps to understand the causes why meniscal lesions (and meniscus extrusion) may lead to cartilage loss and why cartilage loss may also induce meniscal damage. In turn, the reconstructive surgical consequences are also based on these topographical correlations.

The type of approach does not influence TKA component position in revision total knee arthroplasty — A clinical study using 3D-CT

BACKGROUND The influence of the surgical approach on the position of the prosthetic components in revision of total knee arthroplasties (rTKA) is still not clear. This study compared the medial parapatellar approach (MPA) and lateral parapatellar subvastus approach with tibial tubercle osteotomy (LPA). METHODS Forty-two consecutive patients underwent rTKA from 2006 to 2016 with either MPA (n=21) or LPA (n=21) because of aseptic loosening, infection, malposition or instability (mean follow-up: 41.5months). Revision TKA component position and leg alignment were assessed on three-dimensional CT (3D-CT) images and compared between groups using a t-test (p<0.05). Rotation of rTKA components graded into internal, neutral or external rotation and rates of postoperative complications and revisions were compared between groups with a chi2-test (p<0.05). RESULTS Group MPA and LPA showed no significant differences with respect to the femoral component (coronal: 0.6° vs 0.9°; sagittal: 7.5° vs 7.7°; transversal: 0.4° vs -0.2°), tibial component (coronal: 0.1° vs 0.3°; sagittal: 3.1° vs 1.6°; transversal: 6.9° vs 9.3°) and leg alignment (varus: 0.2° vs 1.1°) (p<0.05). Group LPA showed a non-significant (p=0.25) higher incidence of neutrally (28.6% vs 9.5%) and less internally (23.8% vs 38.1%) rotated tibial components. Rates of complication and revisions did not differ significantly. CONCLUSIONS In contrast with primary TKA, the two approaches did not influence postoperative rTKA position. This can be explained with the more extensive approach at rTKA and means that no corrections of the orientation of the components are needed performing either MPA or LPA.

How to Identify the Optimal Surgical Intervention for Your Osteoarthritic Patient (ICL 11)

What is the optimal treatment for your osteoarthritic patient? How do you decide which surgical treatment to choose? What are the treatment options surgically? When to choose what?

Preoperative MR Imaging of the Meniscus

This chapter describes the use of MRI in the diagnosis and preoperative evaluation of meniscal injuries, providing guidance on how to identify a meniscal tear in different sequences and views. MR criteria for a meniscal tear include linearly increased signal intensity contacting the articular surface or penetrating the free edge of the meniscus on at least two consecutive images. Knowledge of normal MR anatomy and its variants is crucial to avoid misinterpretations.

Postoperative Imaging of the Meniscus

This chapter analyzes the different methods for the direct or indirect visualization of the meniscus and the concurrent pathologies present in the knee joint. The visualization of the partial meniscectomy, the meniscus repair, and the meniscus allograft are also presented and discussed.

SPECT/CT Imaging of the Meniscus and Cartilage: What Does It Offer?

MRI is considered as gold standard, and it is the most important imaging for patients with meniscal pathologies. However, nuclear medicine imaging may offer additional information for the orthopaedic surgeon, which could be useful for guidance of the optimal treatment in degenerative knees.

Meniscal Root Tears (ICL 6)

Detailed knowledge about the anatomy of the meniscal roots is crucial when performing root repair, since biomechanical studies have shown that non-anatomic root repair cannot restore native knee joint biomechanics [52, 83]. In addition, meniscal roots are under considerable risk for iatrogenic injuries during different surgical procedures such as meniscal cyst resection, reconstruction of the cruciate ligaments, or intramedullary tibial nailing [24, 55, 56].