Anatomic anterior cruciate ligament (ACL) reconstruction: a global perspective. Part 1.

PURPOSE: In August 2011, orthopaedic surgeons from more than 20 countries attended a summit on anatomic anterior cruciate ligament (ACL) reconstruction. The summit offered a unique opportunity to discuss current concepts, approaches, and techniques in the field of ACL reconstruction among leading surgeons in the field. METHODS: Five panels (with 36 panellists) were conducted on key issues in ACL surgery: anatomic ACL reconstruction, rehabilitation and return to activity following anatomic ACL reconstruction, failure after ACL reconstruction, revision anatomic ACL reconstruction, and partial ACL injuries and ACL augmentation. Panellists' responses were secondarily collected using an online survey. RESULTS: Thirty-six panellists (35 surgeons and 1 physical therapist) sat on at least one panel. Of the 35 surgeons surveyed, 22 reported performing "anatomic" ACL reconstructions. The preferred graft choice was hamstring tendon autograft (53.1 %) followed by bone-patellar tendon-bone autograft (22.8 %), allograft (13.5 %), and quadriceps tendon autograft (10.6 %). Patients generally returned to play after an average of 6 months, with return to full competition after an average of 8 months. ACL reconstruction "failure" was defined by 12 surgeons as instability and pathological laxity on examination, a need for revision, and/or evidence of tear on magnetic resonance imaging. The average percentage of patients meeting the criteria for "failure" was 8.2 %. CONCLUSIONS: These data summarize the results of five panels on anatomic ACL reconstruction. The most popular graft choice among surgeons for primary ACL reconstructions is hamstring tendon autograft, with allograft being used most frequently employed in revision cases. Nearly half of the surgeons surveyed performed both single- and double-bundle ACL reconstructions depending on certain criteria. Regardless of the technique regularly employed, there was unanimous support among surgeons for the use of "anatomic" reconstructions using bony and soft tissue remnant landmarks.

Coronal oblique imaging of the knee: can it increase radiologists' confidence in diagnosing posterior root meniscal tears?

AIM: To investigate the utility of the coronal oblique sequence in the interrogation of posterior root meniscal lesions. MATERIALS AND METHODS: Following international review board approval, 62 consecutive knee arthroscopy cases were referred to the musculoskeletal (MSK) radiologists from the same orthopaedic surgeon for imaging/surgical correlation of the posterior meniscal roots. Of 62 cases, 45 lateral and 46 medial menisci met the inclusion criteria. Imaging evaluation was performed with standard magnetic resonance imaging (MRI) sequences, including a coronal oblique proton density sequence. Two blinded fellowship-trained MSK radiologists independently evaluated the menisci on standard sequences indicating whether a tear was identified and then specifying a confidence score using a scale of 1-3 on each study interpreted. Immediately thereafter, the coronal oblique sequence was evaluated using the same method. Statistics were performed on meniscal lesions involving the posterior horn/root junction or isolated root tears comparing confidence scores. RESULTS: Reader A identified nine posterior horn/root junction tears and 14 isolated root tears. Following the addition of the coronal oblique sequence, confidence scores increased in three of 14 (21.4%) isolated root tears. All three final reads were concordant with arthroscopy. Reader B identified 10 posterior horn/root junction tears and 19 isolated root tears. The confidence score increased in six cases: five of 19 (26.3%) isolated root tears and one of 10 (10%) posterior horn/root junction tears. All six final reads were concordant with arthroscopy. Kappa coefficients indicated near perfect agreement. CONCLUSION: The coronal oblique sequence increased reader confidence in nearly 24% of the posterior root cases identified in this series.

[A comparison of orthopaedic sports medicine education in Germany and the US]. / Ein Vergleich der sportorthopädischen Ausbildung in Deutschland und den USA.

INTRODUCTION: The international exchange of German doctors especially in the US makes it important to compare both educational systems. The goal of this article is to discuss the differences and similarities between the German and US American curricula for Orthopaedic Sports Medicine. METHODS: The German and US American curricula for Sports Medicine and their education and fellowship programs were compared. RESULTS: The title 'Specialist for Sports Medicine' can be obtained in both countries. In Germany the curriculum is not speciality specific but offers a general Sports Medicine education that can be obtained through courses or fellowships. In the US this title can be obtained in two different ways, either through the American Board of Family Medicine (ABFM), or the American Board of Orthopaedic Surgery (ABOS) and their respective fellowship programs. DISCUSSION: The Sports Medicine curriculum in Germany and in the US is different with a general Sports Medicine program in Germany and a specific Sports Orthopaedic program in the US.

Comparative study of the size and shape of human anterior and posterior cruciate ligaments.

As an important step toward determination of the function of cruciate ligaments, the cross-sectional shapes and areas of the anterior cruciate, posterior cruciate, and meniscofemoral ligaments were evaluated in situ within the same knee with use of a laser micrometer system. Measurements were made in eight human cadaveric knees at five levels along the midsubstance of each ligament, with the knee at 0 degree, 30 degrees, 60 degrees, and 90 degrees of flexion. The posterior cruciate ligament was found to be widest in the medial-lateral direction, whereas the anterior cruciate ligament usually was larger in the anterior-posterior direction. The cross-sectional shapes of the anterior cruciate ligament generally were noted to be more circular along the entire midsubstance than were those of the posterior cruciate ligament. In contrast, the cross-sectional shapes of the posterior cruciate ligament were more circular near the tibia, becoming progressively more elongated toward the femur. The meniscofemoral ligaments were more circular than the cruciate ligaments, with an occasional medial-lateral widening similar to that of the posterior cruciate ligament. The cross-sectional area of both the cruciate ligaments changed along the length of the midsubstance, with the anterior cruciate ligament becoming slightly larger distally and the posterior cruciate ligament enlarging proximally. The angle of flexion of the knee was not found to have a significant effect on the cross-sectional areas of the ligaments but was noted to alter the cross-sectional shapes.(ABSTRACT TRUNCATED AT 250 WORDS)

In situ forces in the human posterior cruciate ligament in response to muscle loads: a cadaveric study.

The objectives of this study were to determine the effects of hamstrings and quadriceps muscle loads on knee kinematics and in situ forces in the posterior cruciate ligament of the knee and to evaluate how the effects of these muscle loads change with knee flexion. Nine human cadaveric knees were studied with a robotic manipulator/universal force-moment sensor testing system. The knees were subjected to an isolated hamstrings load (40 N to both the biceps and the semimembranosus), a combined hamstrings and quadriceps load (the hamstrings load and a 200-N quadriceps load), and an isolated quadriceps load of 200 N. Each load was applied with the knee at full extension and at 30, 60, 90, and 120 degrees of flexion. Without muscle loads, in situ forces in the posterior cruciate ligament were small, ranging from 6+/-5 N at 30 degrees of flexion to 15+/-3 N at 90 degrees. Under an isolated hamstrings load, the in situ force in the posterior cruciate ligament increased significantly throughout all angles of knee flexion, from 13+/-6 N at full extension to 86+/-19 N at 90 degrees. A posterior tibial translation ranging from 1.3+/-0.6 to 2.5+/-0.5 mm was also observed from full extension to 30 degrees of flexion under the hamstrings load. With a combined hamstrings and quadriceps load, tibial translation was 2.2+/-0.7 mm posteriorly at 120 degrees of flexion ut was as high as 4.6+/-1.7 mm anteriorly at 30 degrees. The in situ force in the posterior cruciate ligament decreased significantly under this loading condition compared with under an isolated hamstrings load, ranging from 6+/-7 to 58+/-13 N from 30 to 120 degrees of flexion. With an isolated quadriceps load of 200 N, the in situ forces in the posterior cruciate ligament ranged from 4+/-3 N at 60 degrees of flexion to 34+/-12 N at 120 degrees. Our findings support the notion that, compared with an isolated hamstrings load, combined hamstrings and quadriceps loads significantly reduce the in situ force in the posterior cruciate ligament. These data are in direct contrast to those for the anterior cruciate ligament. Furthermore, we have demonstrated that the effects of muscle loads depend significantly on the angle of knee flexion.

In situ forces in the posterolateral structures of the knee under posterior tibial loading in the intact and posterior cruciate ligament-deficient knee.

The posterolateral structures of the knee consist of a complex anatomical architecture that includes several components with both static and dynamic functions. Injuries of the posterolateral structures occur frequently in conjunction with ruptures of the posterior cruciate ligament. To investigate the role of the posterolateral structures in maintaining posterior knee stability, we measured the in situ forces in the posterolateral structures and the distribution of force within the structures' major components, i.e., the popliteus complex and the lateral collateral ligament, in response to a posterior tibial load. Eight cadaveric knees were tested. With use of a robotic/universal force-moment sensor testing system, a posterior tibial load of 110 N was applied to the knee, and the resulting five-degree-of-freedom kinematics were measured at flexion angles of 0, 30, 60, 75, and 90 degrees. The knees were tested first in the intact state and then after the posterior cruciate ligament had been resected. These tests were also performed with an additional load of 44 N applied at the aponeurosis to simulate contraction of the popliteus muscle. In the intact knee, the in situ forces in the posterolateral structures were found to decrease with increasing knee flexion. After the posterior cruciate ligament was sectioned, these forces increased significantly at all angles of flexion. With no load applied to the popliteus muscle, the in situ forces in the popliteus complex were similar to those in the lateral collateral ligament. However, with a load of 44 N applied to the popliteus muscle, in situ forces in the popliteus complex were three to five times higher than those in the lateral collateral ligament. These results reveal that in response to posterior tibial loads, the posterolateral structures play an important role at full extension in intact knees and at all angles of flexion in posterior cruciate ligament-deficient knees. The popliteus muscle appears to be a major stabilizer under this loading condition; thus, the inability to restore its function may be a cause of unsatisfactory results in reconstructive procedures of the posterolateral structures of the knee.

Significance of changes in the reference position for measurements of tibial translation and diagnosis of cruciate ligament deficiency.

Measurements of tibial translation in response to an external load are used in clinical and laboratory settings to diagnose and characterize knee-ligament injuries. Before these measurements can be quantified, a reference position of the knee must be established (defined as the position of the knee with no external forces or moments applied). The objective of this study was to determine the effects of cruciate ligament deficiency on this reference position and on subsequent measurements of tibial translation and, in so doing, to establish a standard of kinematic measurement for future biomechanical studies. Thirty-six human cadaveric knees were studied with a robotic/universal force-moment sensor testing system. The reference positions of the intact and posterior cruciate ligament-deficient knees of 18 specimens were determined at full extension and at 30, 60, 90, and 120 degrees of flexion, and the remaining five-degree-of-freedom knee motion was unrestricted. Subsequently, under a 134-N anterior-posterior load, the resulting knee kinematics were measured with respect to the reference positions of the intact and posterior cruciate ligament-deficient knees. With posterior cruciate ligament deficiency, the reference position of the knee moved significantly in the posterior direction, reaching a maximal shift of 9.3 +/- 3.8 mm at 90 degrees of flexion. For the posterior cruciate ligament-deficient knee, posterior tibial translation ranged from 13.0 +/- 3.4 to 17.7 +/- 3.6 mm at 30 and 90 degrees, respectively, when measured with respect to the reference positions of the intact knee. When measured with respect to the reference positions of the posterior cruciate ligament-deficient knee, these values were significantly lower, ranging from 11.7 +/- 4.3 mm at 30 degrees of knee flexion to 8.4 +/- 4.8 mm at 90 degrees. A similar protocol was performed to study the effects of anterior cruciate ligament deficiency on 18 additional knees. With anterior cruciate ligament deficiency, only a very small anterior shift in the reference position was observed. Overall, this shift did not significantly affect measurements of tibial translation in the anterior cruciate ligament-deficient knee. Thus, when the tibial translation in the posterior cruciate ligament-injured knee is measured when the reference position of the intact knee is not available, errors can occur and the measurement may not completely reflect the significance of posterior cruciate ligament deficiency. However, there should be less corresponding error when measuring the tibial translation of the anterior cruciate ligament-injured knee because the shift in reference position with anterior cruciate ligament deficiency is too small to be significant. We therefore recommend that in the clinical setting, where the reference position of the knee changes with injury, comparison of total anterior-posterior translation with that of the uninjured knee can be a more reproducible and accurate measurement for assessing cruciate-ligament injury, especially in posterior cruciate ligament-injured knees. Similarly, in biomechanical testing where tibial translations are often reported for the ligament-deficient and reconstructed knees, a fixed reference position should be chosen when measuring knee kinematics. If such a standard is set, measurements of knee kinematics will more accurately reflect the altered condition of the knee and allow valid comparisons between studies.

Loss of motion following knee ligament reconstruction.

Loss of motion following knee ligament surgery is a common and potentially serious complication. Loss of extension is most common following anterior cruciate ligament reconstruction, and loss of flexion is most common after posterior cruciate ligament reconstruction. The aetiology of loss of motion is multifactorial and includes impingement and capsulitis. The risk for loss of motion can be minimised by appropriate preoperative, intraoperative and postoperative intervention. Management of loss of motion depends on the cause and length of time following surgery.

Development of a patient-reported measure of function of the knee.

The purpose of the present study was to demonstrate the reliability, validity, and responsiveness of the Activities of Daily Living Scale of the Knee Outcome Survey, a patient-reported measure of functional limitations imposed by pathological disorders and impairments of the knee during activities of daily living. The study comprised 397 patients; 213 were male, 156 were female, and the gender was not recorded for the remaining twenty-eight. The mean age of the patients was 33.3 years (range, twelve to seventy-six years). The patients were referred to physical therapy because of a wide variety of disorders of the knee, including ligamentous and meniscal injuries, patellofemoral pain, and osteoarthrosis. The Activities of Daily Living Scale was administered four times during an eight-week period: at the time of the initial evaluation and after one, four, and eight weeks of therapy. Concurrent measures of function included the Lysholm Knee Scale and several global measures of function. The subjects also provided an assessment of the change in function, with responses ranging from greatly worse to greatly better, at one, four, and eight weeks. The Activities of Daily Living Scale was administered to an additional sample of fifty-two patients (thirty-two male and twenty female patients with a mean age of 31.6 years [range, fourteen to sixty-six years]) before and after treatment within a single day to establish test-retest reliability. Factor analysis revealed two dominant factors: one that reflected a combination of symptoms and functional limitations and the other, only symptoms. The internal consistency of the Activities of Daily Living Scale was substantially higher than that of the Lysholm Knee Scale (coefficient alpha, 0.92 to 0.93 compared with 0.60 to 0.73), resulting in a smaller standard error of measurement for the former scale. Validity was demonstrated by moderately strong correlations with concurrent measures of function, including the Lysholm Knee Scale (r = 0.78 to 0.86) and the global assessment of function as measured on a scale ranging from 0 to 100 points (r = 0.66 to 0.75). Analysis of variance with repeated measures revealed significant improvements in the score on the Activities of Daily Living Scale during the eight weeks of physical therapy (F2,236 = 108.13; p < 0.0001); post hoc testing indicated that the change in the score at eight weeks was significantly greater than the change at four weeks and that the change at four weeks was significantly greater than that at one week (p < 0.0001 for both). As had been hypothesized, the patients in whom the knee had somewhat improved had a significantly smaller change in the score, both at four weeks (F1,189 = 33.50; p < 0.001) and at eight weeks (F1,156 = 22.48; p < 0.001), compared with those in whom the knee had greatly improved. The test-retest reliability coefficient (intraclass correlation coefficient[2,1]) was 0.97. These results suggest that the Activities of Daily Living Scale is a reliable, valid, and responsive instrument for the assessment of functional limitations that result from a wide variety of pathological disorders and impairments of the knee.

Evaluation and treatment of posterior cruciate ligament injuries.

Improved basic science data on the anatomy and biomechanics of the human posterior cruciate ligament have provided the orthopaedic surgeon with new information on which to base treatment decisions. Injuries to the posterior cruciate ligament are reported to comprise approximately 3% of all knee ligament injuries in the general population and as high as 37% in an emergency department setting. While the diagnosis of a posterior cruciate ligament injury can often be made with a physical examination, ancillary studies such as radiographs and magnetic resonance images can be very helpful in detecting associated ligament and bony injuries. In general, most partial (grades I and II) posterior cruciate ligament injuries can be treated nonoperatively. However, surgical reconstruction is usually recommended for those posterior cruciate ligament injuries that occur in combination with other structures. In this review, current surgical techniques of posterior cruciate ligament reconstruction based on anatomic and biomechanical studies will be discussed.

The role of the long head of the biceps muscle and superior glenoid labrum in anterior stability of the shoulder.

The authors conducted a study to determine if the long head of the biceps muscle and its attachment at the superior glenoid labrum play a role in stability of the shoulder in an overhead position. Their study used a dynamic cadaveric shoulder model that simulated the forces of the rotator cuff and long head of biceps muscles as the glenohumeral joint was abducted and externally rotated. Their data suggest that the long head of the biceps muscle contributes to anterior stability of the glenohumeral joint by increasing the shoulder's resistance to torsional forces in the vulnerable abducted and externally rotated position. The biceps muscle also helps to diminish the stress placed on the inferior glenohumeral ligament. Detachment of the superior glenoid labrum is detrimental to anterior shoulder stability as it decreases the shoulder's resistance to torsion and places a greater magnitude of strain on the inferior glenohumeral ligament.

Modification of the Bankart reconstruction with a suture anchor. Report of a new technique.

We assessed the effectiveness of a new suture anchor that has been designed to anchor sutures into a blind, straight hole drilled in bone. The strength of fixation in glenoid bone is 67 N for the No. 0 anchor and suture, and 82 N for the No. 2 device with suture. During 1988 and 1989, 32 patients underwent a modified Bankart reconstruction for recurrent anterior glenohumeral instability at two centers as part of a prospective study of this modified technique. There were no complications as a result of the technique. The four surgeons involved agreed that the suture anchor simplified the procedure. Seventeen patients have been reviewed, with more than 1 year followup. Ninety-four percent had good to excellent results according to the Bankart rating scale. There was one recurrent dislocation in a football player.

Cidex-induced synovitis.

Microscopic evidence of inflammation was observed in the synovium of rabbit knees that had been injected with 10 ppm of Cidex (2% glutaraldehyde). Initial changes were synovial hypertrophy, subsynovial edema, and vascular congestion. At concentrations of 100 ppm or greater, focal synovial necrosis, hemorrhage, and gross diffuse synovitis were observed. The degree of synovial inflammation was proportional to the concentration of Cidex. Observation of synovial response versus time demonstrated this reaction to be a chemical synovitis without histologic evidence of a delayed hypersensitivity allergic component. Significant intraoperative levels of Cidex were noted in the rise solutions at several hospitals. When a single rinse is used, the concentration of Cidex present in the rinse basin is 100 to 300 ppm. If the same rinse is used for subsequent cases, the Cidex concentration is on the order of 1,000 ppm by the fifth arthroscopic procedure. If a double rinse is used and the rinse changed with each operative case, the Cidex concentration in the second rinse is less than 10 ppm. After irrigation of the knee joint with 1 liter of saline, the intraarticular concentration of Cidex is less than 10 ppm regardless of the rinse technique.

Biomechanical evaluation of rotator cuff fixation methods.

Initial fixation strength and failure mode for various rotator cuff reattachment techniques (variations of the McLaughlin technique) were evaluated. Repair methods included standard suture (control), reinforced suture [expanded polytetrafluoroethylene (PTFE) patch and polydioxanone (PDS) tape augmentation] and stapling (nonarthroscopic and arthroscopic soft-tissue staples). The average strength of intact rotator cuff tissue (supraspinatus tendon) was also determined. The different rotator cuff repairs, including at least one control, were performed on fresh-frozen human cadaver shoulder pairs. Repairs were tested to failure in pure tension with the shoulder fixed in 60 degrees of abduction. Load and displacement data were normalized to controls, grouped according to failure modes, and statistically analyzed. The two basic failure modes observed were 1) bone failure, or suture tearing through the bone (indicating weak bone stock) and 2) tendon failure, or suture tearing of the rotator cuff. Gross comparisons between intact and repaired tendons indicated that the intact tendon was two to three times stronger than the repaired tendon. Based on the mode of failure and lack of increased strength after repair, the use of staples for cuff attachment is discouraged. PDS tape suture reinforcement did not increase fixation strength. In contrast, PTFE patch suture augmentation demonstrated statistically higher initial failure loads than did the control and was of specific benefit for shoulders with weak bone stock.

Loss of motion after anterior cruciate ligament reconstruction.

We did a retrospective review and follow-up examination to investigate the incidence, risk factors, and outcome of patients who developed loss of motion after arthroscopic anterior cruciate ligament reconstruction. Two hundred forty-four patients with a minimum followup of 1 year were reviewed. Loss of motion (defined as a loss of extension of more than 10 degrees or flexion of less than 125 degrees) was identified in 27 patients for an overall incidence of 11.1%. Factors associated with loss of motion included acute reconstruction (less than 1 month from initial injury), male sex, and concomitant medial collateral ligament repair or posterior oblique ligament reefing or both. Twenty-one patients required surgery to regain their motion; three patients required a second procedure. Twenty-one of 27 patients with loss of motion underwent a detailed followup and were compared with 24 randomly chosen controls who had a normal range of motion after anterior cruciate ligament reconstruction. At followup, patients who experienced loss of motion had a significant decrease in noninvolved to involved knee extension and flexion compared to the control patients. There was no difference between our patients and the controls regarding patellofemoral problems, anterior knee laxity, and functional strength. Sixty-seven percent of patients with loss of motion had a good or excellent result in comparison to 80% of the controls.

Quadriceps strength and functional capacity after anterior cruciate ligament reconstruction. Patellar tendon autograft versus allograft.

Harvesting the central third of the patellar tendon for autograft anterior cruciate ligament reconstruction is thought to compromise quadriceps strength and functional capacity. We compared objective measurements of quadriceps strength and functional capacity in athletes after patellar tendon autograft or allograft anterior cruciate ligament reconstruction. We looked at 33 active male patients (mean age, 24.3 years) who had anterior cruciate ligament reconstructions 12 to 24 months earlier using patellar tendon autograft (N = 15) or allograft (N = 18) techniques. All patients underwent an intensive rehabilitation program. Quadriceps strength and power were assessed by measuring peak torque at 60 and 240 deg/sec, torque acceleration energy at 240 deg/sec, and the quadriceps index using a Cybex II isokinetic testing device. Functional capacity was evaluated based on the results of 3 specially designed functional performance tests and the hop test. Results revealed no significant difference between autograft and allograft groups with respect to any of these parameters. These findings indicate that harvesting the central third of the patellar tendon for autograft anterior cruciate ligament reconstruction does not diminish quadriceps strength or functional capacity in highly active patients who have intensive rehabilitation. Thus, the recommendation to avoid patellar tendon autograft anterior cruciate ligament reconstruction to preserve quadriceps strength and functional capacity may be unnecessary.

Determination of the in situ forces in the human posterior cruciate ligament using robotic technology. A cadaveric study.

We examined the in situ forces in the posterior cruciate ligament as well as the force distribution between its anterolateral and posteromedial bundles. Using a robotic manipulator in conjunction with a universal force-moment sensor system, we applied posterior tibial loads from 22 to 110 N to the joint at 0 degrees to 90 degrees of knee flexion. The magnitude of the in situ force in the posterior cruciate ligament and its bundles was significantly affected by knee flexion angle and posterior tibial loading. In situ forces in the posterior cruciate ligament ranged from 6.1 +/- 6.0 N under a 22-N posterior tibial load at 0 degree of knee flexion to 112.3 +/- 28.5 N under a 110-N load at 90 degrees. The force in the posteromedial bundle reached a maximum of 67.9 +/- 31.5 N at 90 degrees of knee flexion, and the force in the anterolateral bundle reached a maximum of 47.8 +/- 23.0 N at 60 degrees of knee flexion under a 110-N load. No significant differences existed between the in situ forces in the two bundles at any knee flexion angle. This study provides insight into the knee flexion angle at which each bundle of the posterior cruciate ligament experiences the highest in situ forces under posterior tibial loading. This information can help guide us in more accurate graft placement, fixation, and tensioning, and serve as an assessment of graft performance.

Detailed analysis of patients with bilateral anterior cruciate ligament injuries.

To better understand anatomic and other possible predisposing factors for anterior cruciate ligament injuries, we retrospectively studied 31 patients with noncontact, bilateral injuries of this ligament. The 31 patients were carefully matched by age, sex, height, weight, and activity level with 23 control subjects who had no history of knee injury. All 54 subjects underwent a full clinical knee examination, joint hypermobility tests, a hamstring tightness assessment, a computerized tomography scan analysis, and a plain view radiographic analysis, and were asked to provide a complete immediate-family history of knee ligament injury. In addition, the 31 patients in the experimental group underwent a KT-1000 arthrometer knee laxity examination and were also asked to provide an injury profile, including mechanism of injury, treatment received for each injury, and the time interval between injuries. Measurements obtained from the computerized tomography scan analysis demonstrated a significantly wider lateral femoral condyle in the experimental group compared with the control group, indicating that certain anatomic factors may predispose people to anterior cruciate ligament injury. A significant difference was also found in the incidence rate of anterior cruciate ligament injury in the family history of the experimental group compared with the control group, indicating a possible congenital aspect of this injury.

Biomechanical analysis of a double-bundle posterior cruciate ligament reconstruction.

The objective of this study was to experimentally evaluate a single-bundle versus a double-bundle posterior cruciate ligament reconstruction by comparing the resulting knee biomechanics with those of the intact knee. Ten human cadaveric knees were tested using a robotic/universal force-moment sensor testing system. The knees were subjected to a 134-N posterior tibial load at five flexion angles. Three knee conditions were tested: 1) intact knee, 2) single-bundle reconstruction, and 3) double-bundle reconstruction. Posterior tibial translation of the intact knee ranged from 4.9 +/- 2.7 mm at 90 degrees to 7.2 +/- 1.5 mm at full extension. After the single-bundle reconstruction, posterior tibial translation increased to 7.3 +/- 3.9 mm and 9.2 +/- 2.8 mm at 90 degrees and full extension, respectively, while the corresponding in situ forces in the graft were up to 44 +/- 19 N lower than those in the intact ligament. Conversely, with double-bundle reconstruction, the posterior tibial translation did not differ significantly from the intact knee at any flexion angle tested. This reconstruction also restored in situ forces more closely than did the single-bundle reconstruction. These data suggest that a double-bundle posterior cruciate ligament reconstruction can more closely restore the biomechanics of the intact knee than can the single-bundle reconstruction throughout the range of knee flexion.

The effects of a popliteus muscle load on in situ forces in the posterior cruciate ligament and on knee kinematics. A human cadaveric study.

To investigate the effect of simulated contraction of the popliteus muscle on the in situ forces in the posterior cruciate ligament and on changes in knee kinematics, we studied 10 human cadaveric knees (donor age, 58 to 89 years) using a robotic manipulator/universal force moment sensor system. Under a 110-N posterior tibial load (simulated posterior drawer test), the kinematics of the intact knee and the in situ forces in the ligament were determined. The test was repeated with the addition of a 44-N load to the popliteus muscle. The posterior cruciate ligament was then sectioned and the knee was subjected to the same tests. The additional popliteus muscle load significantly reduced the in situ forces in the ligament by 9% to 36% at 90 degrees and 30 degrees of flexion, respectively. No significant effects on posterior tibial translation of the intact knee were found. However, in the ligament-deficient knee, posterior tibial translation was reduced by up to 36% of the translation caused by ligament transection. A coupled internal tibial rotation of 2 degrees to 4 degrees at 60 degrees to 90 degrees of knee flexion was observed in both the intact and ligament-deficient knees when the popliteus muscle load was added. Our results indicate that the popliteus muscle shares the function of the posterior cruciate ligament in resisting posterior tibial loads and can contribute to knee stability when the ligament is absent.