Passive Knee Motion Research Articles

A novel 3D parallel mechanism for the passive motion simulation of the patella-femur-tibia complex

Parallel mechanisms have been exploited for the kinematic modelling of the passive motion, i.e. the motion under virtually unloaded conditions, of the patella-femur-tibia human joint. In particular, a new mechanism is devised in this paper: a 3D model of the patella-femur relative motion is presented which, combined with a previous simplified model of the femur-tibia relative motion, provides a suitable tool for the design of knee prostheses. Although less accurate than a previously presented model of the patella-femur-tibia joint, the new mechanism still replicates passive knee motion quite well and is simpler from a mechanical point of view. Experimental results validate the efficiency of the proposed model.

Pattern of Motion Restriction in Nigerian Patients with Knee Osteoarthritis

In the Western population, knee osteoarthritis (OA) has been shown to present a characteristic passive motion restriction pattern, called the capsular pattern (extension restriction to flexion restriction ratio ranging from 0.03 to 0.50). The pattern of motion restriction of Nigerian patients with OA has not been previously reported. This study was conducted to determine the pattern of motion restriction in Nigerian patients with knee osteoarthritis. Participants were 50 patients with knee OA (OA Group/OAG), recruited consecutively from two secondary health institutions and 50 age and sex-matched controls (Control Group/CG) without symptoms of OA. Goniometric measurements of passive and active knee motion of participants were taken. Data was analysed using the independent t-test. The OAG, aged 58.1±10.7 years has had OA for 4.0±4.5 years. The CG was aged 55.9±10.3 years. Mean active extension (1.5±5.2°) of the OAG differed significantly (P < 0.05) from that of the CG (0°), but the two groups did not differ significantly in passive extension (OAG = 1.2°±4.4°; CG = 0°). The CG (125.9°±4.6°) had significantly higher (P= 0.0001) active knee flexion than the OAG (99.9°±15.5°). Passive knee flexion of the CG (134.5°±5.0°) was significantly higher (P=0.000) than that of the OAG (110.4°±14.8°). Mean active extension and flexion restriction of OAG was 2.1±5.7° and 26.0±15.4° respectively. Mean passive extension restriction was 1.2±4.4° and passive flexion restriction was 24.0±14.8°, giving a ratio of 0.05 for OAG. Our findings suggest that the passive motion restriction pattern seen in Nigerian patients with knee osteoarthritis is the capsular pattern. KEY WORDS: motion restriction, patients, knee osteoarthritis

Rapid repetitive passive movement improves knee proprioception

Background Proprioception can be affected by many factors including exercise. Most exercises involve certain degrees of repeated passive movements, and different velocities of these movements might affect proprioception differently. The purpose of this study was to evaluate the influences of different angular velocities of repeated passive movement on knee proprioception via active repositioning and kinesthesia measurement. Methods A quasi-experimental design with repeated measure on movement velocity (0°/s, 2°/s, 90°/s, and 150°/s). Sixteen healthy young adults participated in the study. All of them received 30 times repeated passive knee movement intervention in four different knee angular velocities – 0°/s, 2°/s, 90°/s, and 150°/s – with counter-balanced sequence in four successive days. Knee active repositioning and kinesthesia were measured with error scores before and after the intervention. Findings The results revealed a decrease in error scores in both active repositioning and kinesthesia measurement with the velocities of 90°/s and 150°/s (p < 0.05); however no significant change was seen with the static condition (0°/s ) or with the velocity of 2°/s. Interpretation We concluded that repeated passive movement with rapid angular velocities was capable of improving knee proprioception, specifically in active repositioning and kinesthesia measurements. These results would provide information on the effects of different movement velocities onto knee proprioception. Along with further investigations, the findings could potentially enhance our knowledge on knee injury prevention, treatment, and rehabilitation.

Graft length change and radiographic assessment of femoral drill hole position for medial patellofemoral ligament reconstruction

Medial patellofemoral ligament (MPFL) reconstruction has been recognized as a useful treatment method for patella instability. However, the optimal fixation site has not been well investigated, and few reports have examined intraoperative graft length change. The purpose of the study is to evaluate the intraoperative graft length change and femoral drill hole position to find the optimal graft placement. The graft length change between the two points on patella and femur was measured using Isotac(®) and Isometric Positioner(®) during passive knee motion in 27 cases of MPFL. The location of Isotac(®) was also evaluated on the 2-directional radiograph. The pre- and postoperative radiographic assessments have been done in order to evaluate the effect of MPFL reconstruction on patellofemoral alignment. There were 10 cases in which the distance between the two points became longer during knee flexion, 8 cases in which it became shorter and the remaining 9 cases in which the distance changed within 2mm. The femoral drill hole position was assessed assuming that the maximum anterior-posterior (AP) diameter of the femur on the lateral radiograph was defined as 100%. The distance of the femoral tunnel position from the articular surface averaged 50% overall, 46% in the short group, 55% in the longer group and 48% in the isometric group (P<0.001). Patella height seemingly affected the length change character. The intraoperative length change influenced the early recovery of knee range motion postoperatively. The femoral tunnel position is reaffirmed to be an essential determinant for the graft length change in the MPFL reconstruction. Both graft length change measurements and intraoperative radiographic assessment are practical for proper graft placement.

Passive knee movement-induced modulation of the soleus H-reflex and alteration in the fascicle length of the medial gastrocnemius muscle in humans

In humans, an inhibitory via Ia afferent pathway from the medial gastrocnemius (MG) to the soleus (SOL) motoneuron pool has been suggested. Herein, we examined the relation between MG fascicle length changes and the SOL H-reflex modulation during passive knee movement. Twelve subjects performed static and passive (5° s −1) knee movement tasks with the ankle immobilized using an isokinetic dynamometer in sitting posture. The maximal H- and M-waves were measured at four target angles (20°, 40°, 60°, and 80° flexion from full knee extension). The MG fascicles length and velocity were measured using a B-mode ultrasonic apparatus. Results demonstrated that the SOL Hmax/Mmax; i.e., ratio of the maximal H- to M-waves, was attenuated with increasing MG fascicle length in static tasks. The SOL Hmax/Mmax at 20° was significantly attenuated compared with 60° and 80° with increasing MG fascicle length and lengthening velocity in passive knee extension. However, no significant differences in the SOL Hmax/Mmax were found across the target angles in the passive knee flexion task. In conclusion, as muscle spindles increase their discharge with lengthening fascicle velocity, but keep silent when fascicles shorten, our data suggest that lengthening the MG facilitates an inhibitory Ia pathway from MG to SOL, and modulates SOL motoneuron activity during movements.

Continuous epidural analgesia versus continuous intravenous analgesia with peri-articular infiltration following total knee arthroplasty in geriatric patients.

Postoperative continuous intravenous analgesia may not provide effective postoperative analgesia following total knee arthroplasty. This study was conducted to determine if combined continuous intravenous analgesia and peri-articular infiltration provided a better quality of analgesia following total knee arthroplasty than epidural analgesia. A prospective, double-blind study involving 50 patients who had undergone total knee arthroplasty was conducted. Patients were divided into control group and an experimental group. Patients in the control group (n = 25) received peri-articular infiltration with 47 mL normal saline prior to closure of the wound and postoperative epidural analgesia for 48 hours. Patients in the experimental group (n = 25) received a mixture of peri-articular infiltration of 16 mL of 0.75% ropivacaine, 6 mg morphine, 0.2 mg of epinephrine and 25 mL normal saline prior to closure of the wound and postoperative continuous intravenous analgesia for 48 hours. The analgesic efficacy was then evaluated using the verbal numeric rating scale at 1, 2, 6, 12, 24, and 48 hours postoperatively. The side effects and the dosage of rescue analgesics were then recorded. The experimental group showed a significantly higher pain score than the control group 2 and, 6 hours postoperatively at rest and 2 hours postoperatively following passive knee movement (P < 0.05). In addition, the rescue analgesic requirement was higher for the experimental group during the first 24 hours following surgery than for the control group (P < 0.05). We found that combined continuous intravenous analgesia and peri-articular infiltration of a mixture of ropivacaine and, morphine injected into the peri-articular tissue provided minimal benefits for pain control during the early postoperative period when compared to epidural analgesia after total knee arthroplasty.

Efeito de informação sensorial adicional na propriocepção e equilíbrio de indivíduos com lesão do LCA

OBJETIVO: Investigar o efeito da utilização de informação sensorial adicional na propriocepção e no equilíbrio de indivíduos com lesão do Ligamento Cruzado Anterior (LCA). MÉTODOS: Participaram deste estudo 28 indivíduos com lesão unilateral do LCA e 28 indivíduos com joelhos sadios. A propriocepção foi avaliada por meio do limiar para detecção de movimento passivo da articulação do joelho nas posições de 15 e 45 graus, para as direções de flexão e de extensão. O equilíbrio foi avaliado em posição unipodal sem visão, sobre uma plataforma de força e investigado por meio da amplitude e da velocidade média de oscilação do centro de pressão. As condições de informação sensorial utilizadas foram: informação normal, bandagem infra-patelar e faixa infra-patelar. RESULTADOS: Indivíduos com lesão do LCA apresentam um prejuízo na propriocepção e no equilíbrio quando comparados a indivíduos com joelhos sadios (p&lt;0,05). Entretanto, com adição de informação sensorial, tanto a capacidade proprioceptiva quanto o equilíbrio de indivíduos com lesão do LCA é melhorado (p&lt;0,05). Indivíduos com joelhos sadios não apresentam benefício na utilização de informação sensorial adicional (p&gt;0,05). CONCLUSÃO: A lesão do LCA acarreta um prejuízo da propriocepção e do equilíbrio, porém estes efeitos são minimizados com utilização de informação sensorial adicional.

Development of a Passive Knee Motion Simulator to Evaluate Deep Knee Flexion of Total Knee Prosthesis

To evaluate motions and joint reaction forces of the total knee prosthesis during deep knee flexion such as kneeling and sitting straight, a simulator that reproduces the passive motion of the knee has been developed. The main feature of the simulator is that the knee joint is accurately and repeatedly moved from 0° to 180° flexion angle in six degrees of freedom. Moreover, the tibiofemoral and patellofemoral motion and joint reaction forces can be continuously measured. Assuming that muscular force is mainly generated with a quadriceps femoris muscle, the similar force vector is produced by two motors. The custom-designed posterior stabilized type total knee prosthesis which can be flexed to 180° has been inserted in the bone model and evaluated. As a result, it was confirmed that this simulator was able to measure the motion and joint reaction force of the knee with high repetition accuracy. The experimental results showed the same tendency with those in the previously performed cadaveric experiment. Hereafter, cadaver knee can be used for the evaluation of the knee prosthesis using the proposed simulator with high accuracy.

Estimation of Passive Stiffness and Viscosity in Paraplegic: A Dynamic Leg Model in Visual Nastran

This paper presents investigations into pendulum test to measure passive knee motion from a paraplegic subject. The test is used to evaluate changes in the knee angular displacement, passive stiffness and viscosity. Then, genetic algorithm (GA) parameter optimization is used with Visual Nastran (Vn4D) to find passive stiffness and viscosity values for modelling the paraplegic leg. The best performance of the Vn4D leg model is achieved with the optimum values of the viscosity and the stiffness equal to 0.0031055 Nms/deg and 0.024244 Nm/deg respectively. The model was found to be the best Vn4D model with actual subject's leg properties to represent paraplegic leg model.

Physical Function and Properties of Quadriceps Femoris Muscle in Men With Knee Osteoarthritis

Liikavainio T, Lyytinen T, Tyrväinen E, Sipilä S, Arokoski JP. Physical function and properties of quadriceps femoris muscle in men with knee osteoarthritis. Objectives To examine the objective physical function of the lower extremities, to measure the properties of quadriceps femoris muscle (QFM), and to assess subjective disabilities in men with knee osteoarthritis (OA) and to compare the results with those obtained from age- and sex-matched control subjects. Design Cross-sectional study. Setting Rehabilitation clinic in a university hospital. Participants Male volunteers (n=54) (age range, 50–69y) with knee OA and randomly selected healthy, age- and sex-matched control subjects (n=53). Interventions Not applicable. Main Outcome Measures Physical function evaluated with a test battery including the QFM composition measurement, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and the RAND 36-Item Short-Form Health Survey, version 1.0. Results Knee OA patients had 13% to 26% poorer ( P range, .050–.001) physical function and muscle strength compared with the controls. There were also significant differences in QFM composition. WOMAC ( P range, .050–.001) and muscle strength ( P<.001) associated with physical function tests, but subjective pain correlated with neither physical function nor muscle strength in knee OA patients. The radiographic knee OA grade did not have any significant effect on physical function, but passive knee motion, knee extension strength, and WOMAC were related to the severity of the disease ( P<.05). Conclusions The patients with knee OA exhibited impaired physical function and muscle strength and QFM composition compared with healthy controls. The severity of radiographic knee OA clearly had adverse effects on functional ability at the later stages of the disease. The results highlight the effect of QFM strength on physical function as well as the importance of patient's subjective and objective physical function when deciding on knee OA treatment policy.

Three-dimensional knee model: Constrained by isometric ligament bundles and experimentally obtained tibio-femoral contacts

The purpose of this study is to investigate the effect of anterior portion of anterior cruciate ligament, posterior cruciate ligament, anterior and deep portions of medial collateral ligament and the tibio-femoral articular contacts on passive knee motion. A well-accepted reference model for a normal tibio-femoral joint is reconstructed from the literature. The proposed three-dimensional dynamic tibio-femoral model includes the isometric fascicles, ligament bundles and irregularly shaped medial-lateral contact surfaces. With the approach we aim to analyze bone shape and ligament related abnormalities of knee kinematics. The rotations, translations and the contact forces during passive knee flexion were compared against a reference model and the results were found in close accordance. This study demonstrated that isometric ligament bundles play an important role in understanding the femur shape from contact points on tibia. Femoral condyles are not necessarily spherical. The surgical treatments should consider both ligament bundle lengths and contact surface geometries to achieve a problem free knee kinematics after a knee surgery.

The pendulum test as a tool to evaluate passive knee stiffness and viscosity of patients with rheumatoid arthritis

BackgroundThe pendulum test of Wartenberg is a technique commonly used to measure passive knee motion with the aim to assess spasticity. We used this test to evaluate changes of the knee angular displacement, passive stiffness and viscosity in rheumatoid arthritis patients. Stiffness and viscosity represent passive resistances to joint motion associated with the structural properties of the joint tissue and of the muscular-tendon complex. Stiffness can be considered an intrinsic property of the tissues to resist deformation, while viscosity is related to cohesive forces between adjacent layers of tissues. Both parameters may influence the joint range of motion affecting angular displacement.MethodsNine women with rheumatoid arthritis were compared with a group of healthy women. With the subject half-lying, the relaxed knee was dropped from near-full extension and the characteristics of the ensuring damped unsustained knee oscillation evaluated. The kinematics of leg oscillations was recorded using ultrasonic markers (Zebris CMS HS 10) and the kinetic data were calculated from kinematic and anthropometric measures.ResultsKnee stiffness significantly increased (p < 0.001) in patients with respect to the control group, while differences in viscosity were not significant. Moreover, the amplitudes of first knee flexion (the maximal flexion excursion after knee release) and first knee extension (the maximal extension excursion after the first knee flexion) were significantly decreased (p < 0.001). A regression analysis showed that disease severity correlated moderately with stiffness (R2 = 0.68) and first flexion (R2 = 0.78). Using a multivariate regression, we found that increasing stiffness was the main factor for the reduction of flexion and extension motions.ConclusionWe showed that the Wartenberg test can be considered a practical tool to measure mechanical changes of knee caused by rheumatoid arthritis. This novel application of Wartenberg test could be useful to follow up the effects of pharmacological and rehabilitative interventions in this disease.

Mechanics of the passive knee joint. Part 1: The role of the tibial articular surfaces in guiding the passive motion

The motion of the unloaded knee is associated with tibial internal rotation and femoral posterior translation. Although it is known that the passive motion is the result of the interaction between the articular surfaces and the ligaments, the mechanism through which the particular pattern of motion is guided is not completely understood. The goal of this study was to focus on the tibial geometry and to identify the roles that its geometric features have in guiding the passive knee motion. The method used in this study simplified the geometry of the tibial plateaux and the menisci into basic features that could be eliminated individually. The generated tibial geometry was implemented in a computer model to simulate the passive motion. Different parts of the geometry were eliminated individually and the comparison between the simulation results was used to identify the role that each part of the geometry had in guiding the passive motion. The medial meniscus was found as the feature that promoted the tibial internal rotation and restrained the femoral posterior translation. The lateral meniscus and the medial aspect of the tibial eminence, on the other hand, were found as the elements that confined the tibial internal rotation.

The Effects of Varied Joint Motion and Loading Conditions on Posterior Cruciate Ligament Fiber Length Behavior

Background The posterior cruciate ligament has been described as being composed of 2 bands that reciprocally tighten and loosen with knee flexion, but the fiber anatomy and behavior may be more complex. Hypothesis The mechanical effects of defined loading conditions at discrete knee joint angles can vary significantly within the substance of the posterior cruciate ligament depending on the fiber region tested. Study Design Controlled laboratory study. Methods Nine intact, fresh-frozen cadaveric knees were instrumented with excursion filaments implanted within 4 fiber regions of the posterior cruciate ligament. Patterns of fiber behavior were analyzed as a function of the variable linear separation distance between tibial and femoral fiber attachment sites during joint motion under a simulated quadriceps contraction, tibial internal rotation, and tibial external rotation. Analysis of variance, the Newman-Keuls multiple comparisons procedure, and paired t tests were used to evaluate statistical significance. Results Compared with the control pattern of fiber behavior during unloaded passive knee motion from 0° to 120°, the quadriceps force caused loosening of most ligament fibers at knee flexion of less than 75°. Tibial internal rotation significantly slackened the anterior and central fiber regions near extension and significantly tightened the central and posterior fiber regions with progressive flexion. External rotation had an effect similar to internal rotation on the anterior and central fiber regions but caused significant slackening of the posterior fiber regions from 0° to 45°. Conclusions Distinct geographic regions within the posterior cruciate ligament have different functional roles depending on the joint angle and the type of load to which the knee is subjected. Clinical Relevance The specific graft placement parameters in a given surgical procedure relate to end-to-end length changes of the graft and may have important implications for postoperative rehabilitation and return to specific functional activities.

Analysis of forces of ACL reconstructions at the tunnel entrance: is tunnel enlargement a biomechanical problem?

Bone tunnel enlargement is a common phenomenon following reconstruction of the anterior cruciate ligament (ACL). Biomechanical and biological factors have been reported as potential causes of this problem. However, there is no analysis of forces between the graft and bone, as the graft changes direction at the bone tunnel entrance. The purpose of this study was to study these ‘redirecting forces’. Magnetic resonance images of 10 patients with an ACL reconstruction (age: 26±6.8 years) were used to determine the angle between graft and drill holes. Vector analysis was used to calculate the direction and magnitude of the perpendicular component of the force between the bone tunnel and the graft at the entrance of the bone tunnel. Force components were projected into the radiographically important sagittal and coronal planes. Tension of ACL reconstructions was recorded during passive knee motion in 10 cadaveric knee experiments (age: 28.9±10.6 years) and the tension multiplied with the force component for each plane. Results are reported for the coronal and sagittal planes, respectively: For −10° of extension, the percentages of graft tension were determined to be 17±7 (max: 26; min: 7%) and 26±9 (max: 39; min: 16%) for the tibia. They were 59±6 (max: 66; min: 48%) and 99±1 (max: 1.00; min: 99%) for the femur. Force components were 14.68±6.54 and 25.73±12.96 N for the tibial tunnel. For the femoral tunnel, they were 52.48±19.03 and 90.77±32.06 N. Percentages of graft tension and force components were significantly higher for the femoral tunnel compared with the tibial tunnel. Moreover, in the sagittal direction, force components for the femoral tunnel were significantly higher compared with the coronal plane (Wilcoxon test, p<0.01). The differences in force components calculated in this study corresponds with the amount of tunnel enlargement in the radiographic planes in the literature providing evidence that biomechanical forces play a key role in postoperative tunnel expansion.

Spastic velocity threshold constrains functional performance in cerebral palsy

Tuzson AE, Granata KP, Abel MF. Spastic velocity threshold constrains functional performance in cerebral palsy. Arch Phys Med Rehabil 2003;84:1363–8. Objectives: To evaluate a quantitative, velocity-based assessment of spasticity in the quadriceps and hamstrings muscles of children with cerebral palsy (CP) and to show the effects of spasticity in constraining knee velocities during fast gait. Design: A quantitative comparison of neuromuscular and biomechanical performance in patients with CP and controls without CP. Setting: Movement analysis laboratory within a university clinical referral center. Participants: A convenience sample of 18 ambulatory patients with CP and 11 control subjects without CP. Interventions: Not applicable. Main Outcome Measures: Spastic threshold velocity recorded from electromyographic response during passive isovelocity knee movement was compared with knee angular velocity during fast walking, Gross Motor Function Measure (GMFM) scores, and Ashworth Scale score. Results: Patients with measurable spasticity showed slower peak knee angular velocity during walking than patients without spasticity ( P<.005). A significant correlation existed between spastic threshold velocity and peak knee angular velocity during fast walking ( r=.85, P<.001). Spastic threshold velocity correlated significantly with GMFM ( r=.58, P<.05) but not with Ashworth score. Conclusions: The velocity dependency of spasticity can be measured by electromyograph and dynamometer to determine spastic threshold velocity. Spastic threshold velocity correlated with limitations in joint angular velocity during walking and functional performance.

Poster 93: Reliability of the isokinetic measurements of resistance to passive knee motion and the influence of hip angle on peak torque values in healthy subjects

Objectives: To determine (1) the test-retest reliability of the isokinetically measured resistance to passive knee flexion and extension movements at different angular velocities and (2) the impact of different hip angles on the measurements. Design: Cross-sectional study. Setting: Outpatient rehabilitation facility. Participants: 30 healthy volunteers (20 women, 10 men) between the ages of 21 and 39 years. Interventions: Resistance to passive knee flexion and extension movements at 60°, 120°, 180°, and 300°/s were performed twice in the sitting position (hip at 90° of flexion) with a 20-minute interval between the 2 tests. The same procedure was performed in the supine position (hip at full extension). Main Outcome Measures: Peak torque measured the resistance to passive knee motion. Results: The intraclass correlation coefficients (ICCs) ranged between .25 and .65 and .23 and .52, respectively, when the results of the 2 sitting and 2 supine position tests were compared. The ICCs ranged between .22 and 0.6 and .15 and .59 when the results of the sitting and supine position tests were compared in the first and second measurements, respectively. Conclusions: The measurements of resistance to passive knee motion by isokinetic dynamometry were not reliable. Hip position during testing, for example, in the sitting and supine position seemed to have an effect on peak torque values, but because the values for 2 consecutive sitting or supine positions already differed, the difference cannot be directly attributed to changes in the hip position.

Proprioceptive and behavior impairments in individuals with anterior cruciate ligament reconstructed knees

Bonfim TR, Jansen Paccola CA, Barela JA. Proprioceptive and behavior impairments in individuals with anterior cruciate ligament reconstructed knees.Arch Phys Med Rehabil 2003;84:1217–23. Objective: To assess sensory deficits and their effects on proprioceptive and motor function in patients who had undergone unilateral anterior cruciate ligament (ACL) reconstruction. Design: Four evaluations were conducted: (1) joint position perception of the knee for predetermined angles (0°, 15°, 30°, 45°, 60°); (2) threshold for detection of passive knee motion at 0°, 15°, 30°, 45°, and 60° moving into flexion and at 15°, 30°, 45°, and 60° moving into extension; (3) latency onset of hamstring muscles; and (4) postural control during upright double- and single-leg stance. Setting: Movement laboratory in Brazil. Participants: Ten participants who had surgical reconstruction of the ACL (reconstructed group) and 10 participants without knee injury (control group). Interventions: Not applicable. Main Outcome Measures: Absolute error, angular displacement, hamstring muscles latency, and mean sway amplitude. Results: Individuals with a reconstructed knee showed decreased joint position perception, a higher threshold for detection of passive knee motion, longer latency of hamstring muscles, and decreased performance in postural control. Conclusions: After lesion and ACL reconstruction, sensory and motor behavior changes were still observed. This may be because of the lack of proprioceptive information resulting from the ACL lesion and/or substitution of ACL by the graft.

Patellar fracture after reconstruction of the anterior cruciate ligament--case report

The most frequent procedure in treatment of acute or chronic anterior cruciate ligament (ACL) rupture is the so called bone-tendon-bone reconstruction. A transverse dislocated patella fracture is a rare complication of this procedure with an incidence of 0.23%-2.3%. In a five year period, (1998-2002), 407 arthroscopic reconstructions of the anterior cruciate ligaments were done at our Clinic, and there was only one case of patella fracture. An 18-year-old female patient, a handball player, suffered an acute rupture of anterior cruciate ligament of the left knee, so arthroscopic bone-tendon-bone reconstruction of the anterior cruciate ligament was performed. After adequate skin incision, a bone graft was taken from the patella and upper part of trapezoid tibia, which was 25 mm long, 10 mm wide and 5 mm thick, together with a part of patellar ligament. After the remains of the anterior cruciate ligament had been arthroscopically removed, tunnels were made in tibia and femur and a graft was inserted and fixed with two metal interference screws. Knee stability was tested, and drainage was put in the knee joint. The wound was closed by layers. The quadriceps exercises and passive knee movements started immediately. Full range of movements was accomplished six weeks later when the patient started to walk with full weight-bearing on her operated leg. Three weeks later, (nine weeks after the operation), the patient has accidentally lost her balance and fell. A transverse, dislocated fracture of the left patella was diagnosed and osteosynthesis of the fractured patella with two Kirschner wires and a metallic loop was performed. Postoperatively, full range of movement was allowed. Six months later, the patient felt no pain, there was no swelling, full range of knee movement was achieved, while the Lachman Test was identical in both knees and the pivot shift test was negative. Fracture of patella after ACL reconstruction is due to several reasons: size and shape of the graft, technique of its taking, disturbed patellar blood supply, incomplete filling of patella defect after graft taking, and inappropriate postoperative rehabilitation. If a patellar fracture occurs after anterior cruciate ligament reconstruction, the best treatment is firm osteosynthesis, which enables bone healing and immediate continuation of the previously resumed rehabilitation program. However, this complication prolongs the rehabilitation period and slows down return to sports.

Cruciate fracture of the distal femur: the double Hoffa fracture

A 20-year-old woman was involved in a 50 mph head on impact in a motor vehicle crash and taken to an outside hospital. Her main injuries were a closed fracture of left femur (AO-OTA 32C), a closed intercondylar fracture of the right femur (AO-OTA 33C2.3) and an open fracture of the right clavicle. There was no neuro-vascular compromise and no head or visceral injury. Following initial resuscitation, her fractures were stabilised operatively three hours after injury. An unreamed left femoral nail, a reconstruction plate for the left clavicle and a dynamic condylar screw (DCS) to the right distal femur were performed. The DCS was inserted through a routine lateral approach and the fracture primarily bone grafted. Initially, the significance of the coronal fractures in the right distal femur (Fig. 1) was not appreciated. She made an uneventful post operation recovery and was allowed home. After 3 weeks, she attended with increasing pain and deformity in the right knee. Radiograph showed failure of fixation right distal femur fixation (Fig. 2) and she was referred to our centre for specialist reconstruction. Revision fixation via the normal lateral approach proved difficult due to early healing in the fracture gaps and a tibial tubercle osteotomy was required to expose the intra-articular fragments. This revealed displaced Hoffa fractures of both femoral condyles in addition to the intercondylar split, together forming a cruciate fracture pattern. After removal of the previous implants, the condylar fragments were reconstructed using two antero-posterior screws 3.5 mm small fragment cortical lag screws in each condyle. The complete distal articular block was then reconstructed with two further 3.5 mm cortical screws passed from the lateral to medial. After reconstruction there was a virtually anatomic articular surface with minimal structural bone loss. Having converted the ‘‘C’’ to an ‘‘A’’ type injury the metaphyseal element of the fracture was stabilised using the LISS-DF (Less Invasive Stabilisation System–—Distal Femur; Synthes). No bone graft was used. Post-operatively, unrestricted active and passive knee movements but touch weight bearing were encouraged and a hinged knee brace applied. At 3 weeks she had regained 30—808 of knee motion and 8 weeks 10—1008. Radiographs (Fig. 3) showed that the fracture had healed and she was able to fully weight bear without discomfort. Injury, Int. J. Care Injured (2004) 35, 828—830