Volkmar Jansson

Impact of Tibial and Femoral Tunnel Position on Clinical Results After Anterior Cruciate Ligament Reconstruction

PURPOSEnThe purpose of this study was to correlate anatomic and nonanatomic tibial and femoral tunnel positions after anterior cruciate ligament (ACL) reconstruction with clinical outcome by use of bone-patellar tendon-bone (BPTB) single-bundle (SB) and semitendinosus-gracilis (STG) double-bundle (DB) techniques.nnnMETHODSnThe 3-dimensional computed tomography scans of 53 patients knees (27 BPTB-SB and 26 STG-DB) were prepared and measured by 2 examiners according to their tibial and femoral tunnel positions. We evaluated these radiologic constructions and measurements by use of the Cohen κ interobserver and intraobserver coefficient for 2 observers. Patients undergoing both techniques were divided into anatomic and nonanatomic reconstructions according to the findings of Zantop and Petersen. We correlated anatomically and nonanatomically reconstructed patients with clinical outcome by the Tegner score, Western Ontario and McMaster Universities Osteoarthritis Index score, International Knee Documentation Committee score, KT-1000 arthrometer (MEDmetric, San Diego, CA), and pivot-shift test in both techniques.nnnRESULTSnThe radiologic constructions and measurements of 53 computed tomography scans were achieved with a good agreement of interobserver and intraobserver coefficients for 2 observers. We found significantly superior clinical outcome in anatomic ACL reconstructions in both techniques in terms of higher clinical scores (Tegner and International Knee Documentation Committee), higher anterior posterior stability, and less pivot shift. We observed the best outcome in anatomic STG-DB reconstructions.nnnCONCLUSIONSnThis investigation showed that better clinical results are associated with anatomic ACL reconstructions.nnnLEVEL OF EVIDENCEnLevel II, prospective comparative study.

Alternative bearing materials for intervertebral disc arthroplasty

The objective of our study was to test alternative polymer-on-polymer articulations for cervical total disc arthroplasty with favourable biotribological properties and the benefit of radiolucency in comparison to the clinically well established metal-on-polyethylene coupling. In vitro wear simulation was performed according to ISO 18192-1:2008 (E) with the clinically introduced activ C cervical artificial disc (Aesculap AG Tuttlingen, Germany) made of UHMWPE/CoCr29Mo6 in a direct comparison to experimental disc articulations made of PEEK, CFR-PEEK and PEK. Each material combination was tested for 10 million cycles with a customised 6 station spinal wear simulator (EndoLab Thansau, Germany). Gravimetric and geometric wear assessment, optical surface characterisation and an estimation of particle size and morphology were performed. The gravimetric wear rate of the clinical reference polyethylene-on-cobalt-chromium was 1.0+/-0.1 mg/million cycles, compared to 1.4+/-0.4 mg/million cycles for PEEK, to 0.02+/-0.02 mg/million cycles for CFR-PEEK and 0.8+/-0.1 mg/million cycles for PEK. In conclusion, a number of different candidate materials for total cervical disc arthroplasty were compared using the same disc design. Whereas the polymer-on-polymer articulation of PEK showed no substantial benefit in comparison to polyethylene-on-cobalt-chromium and whereas natural PEEK tends towards pitting and delamination, the carbon fibre reinforced PEEK demonstrated an excellent wear behaviour with a reduction in order of a magnitude. Therefore, the CFR-PEEK based polymer-on-polymer articulations may be an alternative to polyethylene-on-metal and have a high potential for next generation disc replacements.

Development and validation of a new method for the radiologic measurement of the tibial slope

PurposeThe posterior tibial slope has a huge influence on the kinematics of the knee. In several orthopedic interventions such as high tibial osteotomy and unicondylar or bicondylar knee replacement changing, the tibial slope can result in altered knee mechanics. Therefore, an exact preoperative measurement of the posterior tibial slope is mandatory. Several methods are used on conventional radiographs and CT scans, but until now there is no standard validated method. The aim of this study was to compare several methods and imaging techniques to measure the posterior tibial slope and to establish a standard and reliable measurement method by radiography.MethodsFourteen knees (seven cadavers) were scanned by a 64-slice CT, a 3T-MRI, and true lateral radiographs were performed. The anatomical references (TPAAxa0=xa0tibial proximal anatomical axis; ATCxa0=xa0anterior tibial cortex; PTCxa0=xa0posterior tibial cortex) and the new computed reference (MPAxa0=xa0mean of PTA and ATC) were compared by short as well as long radiographs, CT scan and MRI. The influence of a malrotation in radiographs of the knees was also analyzed.ResultsCT scan and MRI are suitable for the measurement of the medial and lateral posterior tibial slopes, the results of the radiographs varied depending on the method used. The new method (MPA) showed the best correlation to the CT scan (rxa0=xa00.997), even on short radiographs (10xa0cm distal the joint line).ConclusionThe measurement of the posterior tibial slope on a short lateral radiograph using the MPA is a reliable method and should be established as a standard.Level of evidenceDiagnostic study, Level II.

Migration analysis of a metaphyseal anchored short-stem hip prosthesis.

Background and purpose Metaphyseal anchored short-stem hip implants were designed to improve load transmission and preserve femoral bone stock. Until now, only few outcome data have been available and migration studies are one of the few ways of obtaining data that are predictive of implant survival. We therefore evaluated a metaphyseal anchored short-stem hip implant by Ein Bild Roentgen Analyse femoral component analysis (EBRA-FCA). Patients and methods First, the EBRA-FCA method was validated for the short-stem hip implant. Then 80 of the first 100 consecutive implants were evaluated after at least 2 years. Clinical assessment was performed using the WOMAC and the UCLA score. Results After 2.7 (2.0–4.2), years none of the implants had been revised and by that time the stems had subsided by a mean of 0.7 mm (SD 1.8) (95% CI: 0.3–1.1). Of the 80 implants, 78 were stable after 2 years, with 74 being primary stable and 4 showing secondary stabilization after initial subsidence. Continuous migration was seen in only 2 patients. The clinical outcome showed good results with a mean WOMAC of 11 (SD 13) and a mean UCLA score of 7.3 (SD 2.0). [OK?] Interpretation The metaphyseal anchored short-stem hip implant showed good functional results and a high degree of stability after 2 years. The outcome is comparable to that of clinically proven conventional hip implants and if the results are confirmed by long-term studies, short-stem hip arthroplasty might be an alternative for young patients requiring hip replacement.

Sports Activity After Short-Stem Hip Arthroplasty

Background: No data are available about the sports activity of patients with bone-conserving short-stem hip implants. Hypothesis: Patients can return to a good level of sports activity after implantation of a short-stem hip implant. Study Design: Case series; Level of evidence, 4. Methods: The sports activity level of 68 patients (76 hips) after short-stem hip arthroplasty was assessed for a minimum of 2 years after implantation. In addition to the clinical examination, a detailed evaluation of the patients’ sports pattern was obtained. Furthermore, the results were analyzed with regard to gender (female and male) and age (≤55 and >55 years). Results: After a mean of 2.7 years, patients showed a Harris Hip Score (HHS) of 93.6, a Western Ontario and McMaster Universities Arthritis Index (WOMAC) score of 9.5, and a University of California, Los Angeles (UCLA) activity score of 7.6, with each individual participating on average in 3.5 different disciplines after surgery compared with 3.9 before surgery. High-impact activities decreased significantly postoperatively, whereas low-impact activities increased significantly. The duration of the sports activities remained stable, while the frequency actually increased. In contrast, men participated preoperatively in more sports than women (4.3 men vs 3.3 women). However, because of a pronounced decrease in high-impact activities by men, both genders participated in an equal number of sports postoperatively (3.5 men vs 3.5 women). Finally, 45% (n = 31) reported at least one activity that they missed. Most of them were disciplines with an intermediate- or high-impact level. Conclusion: Patients with a short-stem hip implant can return to a good level of activity postoperatively. Participation in sports almost reached similar levels as preoperatively but with a shift from high- to low-impact activities. This seems desirable from a surgeon’s point of view but should also be communicated to the patient before hip replacement.

The Incidence and Clinical Relevance of Graft Hypertrophy After Matrix-Based Autologous Chondrocyte Implantation

Background: Graft hypertrophy is the most common complication of periosteal autologous chondrocyte implantation (p-ACI). Purpose: The aim of this prospective study was to analyze the development, the incidence rate, and the persistence of graft hypertrophy after matrix-based autologous chondrocyte implantation (mb-ACI) in the knee joint within a 2-year postoperative course. Study Design: Case series; Level of evidence, 4. Methods: Between 2004 and 2007, a total of 41 patients with 44 isolated cartilage defects of the knee were treated with the mb-ACI technique. The mean age of the patients was 35.8 years (standard deviation [SD], 11.3 years), and the mean body mass index was 25.9 (SD, 4.2; range, 19-35.3). The cartilage defects were arthroscopically classified as Outerbridge grades III and IV. The mean area of the cartilage defect measured 6.14 cm2 (SD, 2.3 cm2). Postoperative clinical and magnetic resonance imaging (MRI) examinations were conducted at 3, 6, 12, and 24 months to analyze the incidence and course of the graft. Results: Graft hypertrophy developed in 25% of the patients treated with mb-ACI within a postoperative course of 1 year; 16% of the patients developed hypertrophy grade 2, and 9% developed hypertrophy grade 1. Graft hypertrophy occurred primarily in the first 12 months and regressed in most cases within 2 years. The International Knee Documentation Committee (IKDC) and visual analog scale (VAS) scores improved during the postoperative follow-up time of 2 years. There was no difference between the clinical results regarding the IKDC and VAS pain scores and the presence of graft hypertrophy. Conclusion: The mb-ACI technique does not lead to graft hypertrophy requiring treatment as opposed to classic p-ACI. The frequency of occurrence of graft hypertrophy after p-ACI and mb-ACI is comparable. Graft hypertrophy can be considered as a temporary excessive growth of regenerative cartilage tissue rather than a true graft hypertrophy. It is therefore usually not a persistent or systematic complication in the treatment of circumscribed cartilage defects with mb-ACI.

Biomechanical reconstruction of the hip: comparison between modular short-stem hip arthroplasty and conventional total hip arthroplasty.

PurposeShort-stem hip arthroplasty preserves femoral bone stock which includes the femoral neck. This implies that the stem has to follow the anatomy of the femoral neck. Therefore, it has been questioned whether biomechanical reconstruction of the hip can be safely achieved with SHA.MethodsBiomechanical reconstruction of the hip was analysed for 50 modular short-stem hip arthroplasties (SHA) and compared to 50 conventional total hip arthroplasties (THA). Biomechanical parameters were analysed on pre- and postoperative pelvic overviews and compared to those of the contralateral side.ResultsThe position of the acetabular cup (vertical and horizontal hip centre of rotation) changed slightly and was comparable for both groups. Horizontal femoral offset increased more in SHA (6.2xa0mm) than in THA (2.0xa0mm). Compared to the contralateral side it was significantly greater after SHA (+3.6xa0mm) but almost balanced after THA (−0.2xa0mm). Limb length increased with both procedures (8.0xa0mm SHA, 9.1xa0mm THA), but showed a significantly greater discrepancy after SHA (3.3xa0mm) as compared to THA (1.3xa0mm). According to the different implant designs, the stem-shaft axis showed a wider varus-valgus range for SHA (6.2° varus to 8.8° valgus) than for THA (2.6° varus to 3.3° valgus).ConclusionHorizontal femoral offset increased more with modular SHA than with conventional THA, but was within a beneficial range. Restoration of limb length appears more difficult in SHA and has a tendency to prolong limb length, which is probably related to the higher femoral resection level. This should be taken into consideration when considering SHA for a patient as well as during implantation.

Definition and evaluation of testing scenarios for knee wear simulation under conditions of highly demanding daily activities

The objective of our study was the definition of testing scenarios for knee wear simulation under various highly demanding daily activities of patients after total knee arthroplasty. This was mainly based on a review of published data on knee kinematics and kinetics followed by the evaluation of the accuracy and precision of a new experimental setup. We combined tibio-femoral load and kinematic data reported in the literature to develop deep squatting loading profiles for simulator input. A servo-hydraulic knee wear simulator was customised with a capability of a maximum flexion of 120°, a tibio-femoral load of 5000N, an anterior-posterior (AP) shear force of ±1000N and an internal-external (IE) rotational torque of ±50Nm to simulate highly demanding patient activities. During the evaluation of the newly configurated simulator the ability of the test machine to apply the required load and torque profiles and the flexion kinematics in a precise manner was examined by nominal-actual profile comparisons monitored periodically during subsequent knee wear simulation. For the flexion kinematics under displacement control a delayed actuator response of approximately 0.05s was inevitable due to the inertia of masses in movement of the coupled knee wear stations 1-3 during all applied activities. The axial load and IE torque is applied in an effective manner without substantial deviations between nominal and actual load and torque profiles. During the first third of the motion cycle a marked deviation between nominal and actual AP shear load profiles has to be noticed but without any expected measurable effect on the latter wear simulation due to the fact that the load values are well within the peak magnitude of the nominal load amplitude. In conclusion the described testing method will be an important tool to have more realistic knee wear simulations based on load conditions of the knee joint during activities of daily living.

Use of 18F-FDG-PET in the diagnosis of endoprosthetic loosening of knee and hip implants.

IntroductionTo diagnose septic and aseptic loosening 18-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) has been described with good results for hip arthroplasties. The purpose of the present study was to examine whether there is a difference of feasibility in detecting loosening of hip versus knee prostheses by use of 18F-FDG-PET.PatientsThirty-two patients with lower limb arthroplasty complaints (74 components) were studied preoperatively with 18F-FDG-PET. The interpretation of 18F-FDG-PET was done according to evaluated criteria. The final diagnosis based on intraoperative findings in all cases including microbiological examinations.ResultsFor hip arthroplasty sensitivity/specificity of 18F-FDG-PET towards implant loosening was 80%/87%. For infectious loosening of hip endoprostheses sensitivity/specificity was 67%/83%. In knee endoprostheses sensitivity/specificity for loosening was 56%/82% and 14%/89% for infection. The sensitivity of the results for knee and hip joints in regard to infectious versus aseptic loosening was significantly different.ConclusionWe confirm that 18F-FDG-PET is an appropriate tool to diagnose hip arthroplasty loosening. Differing from that 18F-FDG-PET showed a significant lower sensitivity/specificity in detecting septic loosening of knee endoprostheses. It may therefore be necessary to use different methods to diagnose loosening of endoprostheses depending on the type of implant which is examined.

The accuracy of digital templating: a comparison of short-stem total hip arthroplasty and conventional total hip arthroplasty

PurposeSelection of the correct femoral stem size is crucial in total hip arthroplasty for an uncomplicated implantation and good initial stability. Pre-operative templating has been shown to be a valuable tool in predicting the correct implant size. For short-stem total hip arthroplasty (SHA), which recently is increasingly used, it is unknown if templating can be performed as reliable as conventional total hip arthroplasty (THA).MethodsA total of 100 hip arthroplasties, 50 with SHA and 50 with THA, were templated by four orthopaedic surgeons each. The surgeons had different levels of professional experience and performed a digital template of the acetabular and femoral component on the pre-operative radiographs. The results were compared with the truly inserted implant size.ResultsFor the femoral stems the average percentage of agreement (±1 size) was 89.0xa0% in SHA and 88.5xa0% in THA. There was no significant difference among surgeons in the accuracy of templating the correct stem size and no significant difference between templating SHA and THA. For the acetabular component the average percentage of agreement (±1 size) was 75.8xa0%. However, the more experienced surgeons showed a significant higher accuracy for templating the correct cup size than the less experienced surgeons.ConclusionDigital templating of SHA can predict the stem sizes as accurately as conventional THA. Therefore digital templating is also recommendable for SHA, as it helps to predict the implant size prior to surgery and thereby might help to avoid complications.