Johan Bellemans

Predictors of outcome after manipulation under anaesthesia in patients with a stiff total knee arthroplasty

PurposeFlexion in a stiff total knee arthroplasty (TKA) can be improved by manipulation under anaesthesia (MUA). Although this intervention usually results in an improvement in range of motion, the expected result is not always achieved. The purpose of this study is to determine which factors affect range of motion after manipulation in patients with a stiff total knee.MethodsAfter exclusion (nxa0=xa022), the data of 158 patients (138 knees) with a stiff knee after TKA who received a manipulation under anaesthesia between 2004 and 2014 were retrospectively analysed. Pre-, peri- and post-operative variables were identified and examined for their influence on flexion after the manipulation using Kruskal–Wallis and Mann–Whitney U tests and Spearman correlations.ResultsAfter MUA, a mean improvement in flexion of 30.3° was observed at the final follow-up. Preoperative TKA flexion, design of TKA and interval between TKA procedure and MUA were positive associated with an increase in flexion after MUA. MUA performed 12xa0weeks or more after TKA procedure deteriorated the outcome.ConclusionsThree factors, pre-TKA flexion type of prosthesis and interval between TKA procedure and manipulation under anaesthesia, were found to have impact on flexion after TKA and MUA were identified. Results are expected to be inferior in patients with low flexion before TKA procedure or with a long interval (>12xa0weeks) between the TKA procedure and the manipulation under anaesthesia.Level of evidenceIV.

Mechanical Analysis of Extra-Articular Knee Ligaments. Part One: Native knee ligaments

BACKGROUNDnThe aim of this study was to provide a characterization of the tensile properties of the medial collateral ligament (MCL), lateral collateral ligament (LCL), anterolateral ligament (ALL) and medial patellofemoral ligament (MPFL). Our hypothesis was that extra-articular knee ligaments are heterogeneous in nature and possess distinct material properties.nnnMETHODSnMCL (n=12), LCL (n=11), MPFL (n=12) and ALL (n=19) samples from fresh frozen human cadaveric knees were subjected to uniaxial tensile testing to failure and analyzed for their material properties. The elastic modulus (slope of the linear portion of the stress/strain curve), ultimate stress (stress at failure), ultimate strain (strain at failure) and strain energy density (area under the stress/strain curve) were calculated.nnnRESULTSnThe MCL had the highest elastic modulus (441.8±117.2MPa) and was significantly greater than the MPFL (294.6±190.4MPa) and LCL (289.0±159.7MPa) (P<0.05) as well as the ALL (173.7±91.8MPa) (P<0.001). The ultimate stress was significantly higher (P<0.05) for the LCL (83.6±38.1MPa) and MCL (72.4±20.7MPa), relative to the MPFL (49.1±31.0MPa) and ALL (46.4±20.1MPa). The ultimate strain of the LCL (41.0±9.9%) and ALL (37.8±7.9%) were significantly higher (P<0.05) compared to the MCL (22.9±2.5%) and MPFL (22.2±5.6%). The strain energy density of the LCL (15.2±6.4MPa) was significantly greater (P<0.05) than all other ligaments (ALL 7.8±3.1MPa, MCL 7.5±2.9MPa and MPFL 5.0±2.9MPa).nnnCONCLUSIONSnExtra-articular knee ligaments are a heterogeneous group with respect to material characteristics. Each ligament has tensile properties that are significantly different from others and treatment strategies should take these findings into account.

Mechanical Analysis of Extra-Articular Knee Ligaments. Part two: Tendon grafts used for knee ligament reconstruction

OBJECTIVESnThe aim of this study was to provide information about the mechanical properties of grafts used for knee ligament reconstructions and to compare those results with the mechanical properties of native knee ligaments.nnnMETHODSnEleven cadaveric knees were dissected for the semitendinosus, gracilis, iliotibial band (ITB), quadriceps and patellar tendon. Uniaxial testing to failure was performed using a standardized method and mechanical properties (elastic modulus, ultimate stress, ultimate strain, strain energy density) were determined.nnnRESULTSnThe elastic modulus of the gracilis tendon (1458±476MPa) (P<0.001) and the semitendinosus tendon (1036±312MPa) (P<0.05) was significantly higher than the ITB (610±171MPa), quadriceps tendon (568±194MPa), and patellar tendon (417±107MPa). In addition, the ultimate stress of the hamstring tendons (gracilis 155.0±30.7MPa and semitendinosus 120.1±30.0MPa) was significantly higher (P<0.001, respectively P<0.05), relative to the ITB (75.0±11.8MPa), quadriceps tendon (81.0±27.6MPa), and patellar tendon (76.2±25.1MPa). A significant difference (P<0.05) could be noticed between the ultimate strain of the patellar tendon (24.6±5.9%) and the hamstrings (gracilis 14.5±3.1% and semitendinosus 17.0±4.0%). No significant difference in strain energy density between the grafts was observed.nnnCONCLUSIONSnMaterial properties of common grafts used for knee ligament reconstructions often differ significantly from the original knee ligament which the graft is supposed to emulate.

High risk of tunnel convergence during combined anterior cruciate ligament and anterolateral ligament reconstruction

PurposeTo assess the risk of femoral tunnel convergence in combined anterior cruciate ligament (ACL) and anterolateral ligament (ALL) reconstructions. The hypothesis was that a more proximal and anterior orientation of the ALL femoral tunnel should reduce the risk of convergence with the ACL femoral tunnel.Methods15 fresh-frozen cadaver knees were examined. An anatomic ACL femoral tunnel was drilled arthroscopically in each specimen and ALL tunnels were made in two directions: (1) 0° coronal angulation and 20° axial angulation, (2) 30° coronal angulation and 30° axial angulation. Computed tomography scans were performed to investigate tunnel convergence and to measure the minimal distance between tunnels, tunnel length and the LFC width.ResultsTunnel convergence occurred in 20 of 30 cases (67%). Convergence was significantly reduced when tunnels were drilled at 30° coronal and 30° axial angulation (pu2009<u20090.05). The mean length of the ALL tunnel was 15.9xa0mm [95% CI (13.6; 18.1)] and was independent of ALL tunnel angulation. The mean minimal distance between the ALL and ACL tunnel was 3.1xa0mm [95% CI (2.1; 4.1)]. The odds ratio for tunnel convergence was 3.5 for small LFC, relative to large LFC (n.s.)ConclusionA high risk of tunnel convergence was observed when performing combined ACL and ALL reconstructions. The clinical relevance of this work is that the occurrence of tunnel conflicts can be reduced by aiming the ALL tunnel in a more proximal and anterior direction. Surgeons should be aware of this, since tunnel convergence could jeopardize the ACL reconstruction and fixation.

The shape and orientation of the trochlea run more parallel to the posterior condylar line than generally believed

AbstractPurposeThis study was set up to identify the native trochlear geometry and define its relationship with the rotational landmarks of the distal femur.MethodsThe rotational landmarks of the distal femur were analysed on CT-scans of 281 patients with end-stage knee osteoarthritis.ResultsThe anterior trochlear line (ATL) was on average 4.3° (SD 3.3°) internally rotated relative to the surgical transepicondylar axis (sTEA). The ATL was on average 2.1° (SD 3.0°) internally rotated relative to the posterior condylar line (PCL). The relationship between the ATL and the sTEA was statistically different in the different coronal alignment groups (pxa0=xa00.004): 3.9° (SD 3.0°) in varus knees, 4.0° (SD 2.9°) in neutral knees and 5.4° (SD 3.8°) in valgus knees. The lateralisation of the trochlea, represented by the distance between the perpendicular to PCL and the perpendicular to the posterior parallel line to the sTEA, was on average 2.2xa0mm (SD 1.8xa0mm).nConclusionThe ATL was on average 4.3° (SD 3.3°) internally rotated relative to the sTEA and 2.1° (SD 3.0°) internally rotated relative to the PCL. The ATL is more externally orientated in varus knees and more internally rotated in valgus knees. The trochlear groove is lateralised by only 2.2xa0mm when the femoral component is externally rotated.Level of evidenceIII.