Does the peak torque of the hamstring and quadriceps muscles affect the knee laxity measurements in male patients with anterior cruciate ligament rupture?

The aim of the study was to examine whether the peak torque of the hamstring and quadriceps muscles affects the anterior knee laxity measurements in male patients. The study comprised 45 male patients who had a chronic unilateral anterior cruciate ligament (ACL) rupture. Preoperatively, one experienced physiotherapist performed all the KT-1000 examinations. The anterior displacement was registered at 89 Newton. Immediately after the KT-1000 examination, an isokinetic concentric peak torque measurement was performed at 60°/s for both the hamstring and quadriceps muscles. The anterior displacement was significantly larger in the ACL-ruptured knees compared with the noninjured knees (p < 0.001). Patients with strong hamstring muscles on the injured side displayed significantly less knee laxity compared with patients with less strength (p = 0.018). There was an inverse correlation between the peak torque of the hamstring muscles and the KT-1000 anterior laxity measurements in the ACL-ruptured knees (rho = −0.37, p = 0.01). We conclude that male patients with strong hamstring muscles display smaller KT-1000 laxity measurements than patients with less strength. Received: 22 January 2001/Accepted: 24 January 2001     

Effect of flexion angle on coronal laxity in patients with mobile-bearing total knee arthroplasty prostheses

Proper soft tissue tension is one of the important factors in mobile-bearing total knee arthroplasty (TKA). We evaluated varus/valgus laxities, particularly at flexion, which is a key factor in reducing the risk of subluxation and dislocation of bearings to assess the effect that the flexion angle and the presence or absence of the posterior cruciate ligament (PCL) have on laxity in patients with low-contact stress (LCS) prostheses of the PCL-retaining (24 patients, 24 knees) and PCL-sacrificing (24 patients, 24 knees) type designs during extension and flexion. Both types of prosthesis had about 4° laxity at extension and 3° at flexion. PCL-retaining prostheses had significantly less laxity at flexion than at extension (P = 0.0004 in varus, P = 0.0043 in valgus). For good clinical outcomes following TKA, 3°–4° laxity in the varus and valgus orientations is recommended. In addition, the PCL might be involved in flexion and could affect varus/valgus laxity in PCL-retaining prostheses.     

Objective anterior cruciate ligament testing

We examined subjects with the Stryker knee laxity tester as part of the clinical examination to determine its usefulness in evaluating the anterior cruciate ligament. We measured 123 athletes with no history of knee injury, as well as 30 patients with ACL injury proven by arthroscopy, and 11 injured patients with intact ACL at arthroscopy. We recorded anterior and posterior tibial displacement at 20 degrees of knee flexion and 20 lbs force in each direction. Anterior laxity and side to side difference correlated with ACL injury; posterior and total AP laxity did not. In normal subjects, mean anterior laxity was 2.5 mm. Only 8% of normal knees had anterior laxity of 5 mm or more. Ten percent of normal subjects had a side to side difference of 2 mm or more. In ACL tears, mean laxity was 8.1 mm, with 94% measuring 5 mm or more. Of the subjects, 89% with unilateral ACL injury had an increase of 2 mm or more on the injured side. Ten of ten acute ACL tears were detected by these criteria, with no false positives. In injured knees with intact ACL, measurements did not differ significantly from normal. We found the objective knee laxity measurement to be a useful complement to clinical knee examination.     

Bilateral simultaneous anterior cruciate ligament reconstruction: A case series and review of the literature

Bilateral ACL rupture is a relatively uncommon injury with an incidence of 2–4%. Most bilateral ACL rupture occurs at two different times, but few cases of single-staged bilateral ACL ruptures have also been reported. There have been reports of both single-staged, and two-staged reconstruction of bilateral ACL ruptures in the literature but without a clear consensus. We present a series of five bilateral ACL rupture cases managed by single-staged arthroscopic ACL reconstruction, using quadrupled hamstring grafts. All of them were young males, with an average age of 26.8 years (Range: 19–39 years). Three out of five of these cases (60%) had sustained the injury to both the knees simultaneously while playing sports. All the five patients had generalized joint laxity with significant hyperextension of their knees. All the ten knees (in five patients) were clinically stable, at their last follow-ups. None of the knees had any early or late complications. A single-staged bilateral ACL reconstruction is a safe, reproducible, and cost-effective procedure for patients with a bilateral ACL deficient knee, in experienced hands.     

Treatment of the anterior cruciate ligament-absent knee with associated meniscal tears. Instrumented testing and clinical evaluation of two patient groups

The UCLA instrumented clinical testing apparatus was used to measure postoperative stiffness and laxity for two groups of patients with documented chronic absence of the anterior cruciate ligament (ACL) and associated meniscal tears. Group 1 consisted of 76 patients (average age, 25 years) who had undergone anterior cruciate substitution using the torn meniscus, and a second group of 34 patients (average age, 31 years) who had partial meniscectomy alone without ACL substitution. Subjective and objective evaluations were significantly higher and symptoms of pain and buckling significantly lower in the substitution group. In addition, 29% of Group 1 and only 7% of Group 2 patients were able to return to their preinjury sports without limitations, while 5% of the former and 12% of the latter could not return to any sport. At 90 degrees of flexion, there were no significant differences in stiffness or laxity between the patient groups. At 20 degrees of flexion and neutral foot rotation, the meniscal substitution group had an average of 1.4 mm less side-to-side laxity difference than the partial meniscectomy patients; 51% of the substituted patients still had an injured knee laxity that was at least 2 mm greater than the uninjured knee, as contrasted to 67% of the partial meniscectomy patients who exceeded this upper limit of the normal range. At 20 degrees, anterior stiffness of the injured knees of the substitution patients was 28% greater than the injured knees of the partial meniscectomy group; 42% of the substituted patients had an injured knee stiffness within the normal range, while only 18% of the partial meniscectomy patients fell within normal limits. There were no statistical correlations of stiffness or laxity values with clinical scores or patient symptomatology in either group.     

Characteristics of anterior tibial translation with active and isokinetic knee extension exercise before and after ACL reconstruction

 The aim of this study was to investigate the biomechanical characteristics of anterior tibial translation (ATT) in anterior cruciate ligament (ACL)-deficient or -reconstructed knees with active and isokinetic knee extension exercise. Forty-nine patients with unilateral isolated ACL-deficient knees were enrolled. Follow-up examinations were carried out at a mean of 24 months postoperatively. An electrogoniometer system was applied to compare the amount of ATT in ACL-deficient and -reconstructed knees. For both active and isokinetic knee extension, the mean ATT of ACL-deficient knees was considerably greater than that for the normal side, within a range of flexion 0°–70° and 0°–60°, respectively. In contrast, no mean ATT differences were seen during both active and isokinetic exercise from 90° to 0° at follow-up. Within a range of flexion between 50° and 70°, the side-to-side difference in ATT with active knee extension was significantly greater than that with isokinetic extension in ACL-reconstructed knees. These results suggest that the amount of ATT is significantly improved with both active and isokinetic exercise, postoperatively. However, postoperative ATT with isokinetic extension is smaller than that with active knee extension from 50° to 70°. Received: October 17, 2001 / Accepted: December 26, 2001     

Coronal laxity in extension in vivo after total knee arthroplasty

We performed stress arthrometric studies on 77 knees (71 patients) with total knee arthroplasty to determine the presence and magnitude of femoral abduction and adduction in knee extension. A total of 53 knees (49 patients) had posterior cruciate ligament-retaining (PCLR) prostheses, and 24 (22 patients) had PCL-substituting (PCLS) prostheses. The selected patients had successful arthroplasties with no clinical complications a minimum of 5 years after primary surgery. Each patient was subjected to a successive abduction and adduction stress test at 0°–20° of flexion using a Telos arthrometer. The mean values for abduction and adduction were 4.8° and 4.5° with a PCLR prosthesis, respectively, and 4.6° and 4.0° with a PCLS prosthesis. There were no statistical differences between PCLR and PCLS knees. The results suggest that approximately 4° of laxity in these directions is suitable in total knee arthroplasty for a satisfactory clinical outcome 5–9 years after surgery.     

Knee instability after injury to the anterior cruciate ligament. Quantification of the Lachman test

We have measured anterior and posterior displacement in 563 normal knees and 487 knees with chronic deficiency of the anterior cruciate ligament (ACL). We performed stress radiography using a simple apparatus which maintained the knee at 20 degrees of flexion while a 9 kg load was applied. There was no significant difference in posterior translation dependent on the condition of the ACL. Measurement of anterior translation in the medial compartment proved to be more reliable than in the lateral compartment for the diagnosis of rupture of the ACL, with better specificity, sensitivity and predictive values. We have classified anterior laxity based on the differential anterior translation of the medial compartment and identified four grades in each of which we can further distinguish four subgrades for laxity of the lateral compartment. Within each of these subgroups, either internal or external rotation may dominate and sometimes there is a major translation of both compartments. Radiological evaluation of displacement of the knee in 20 degrees of flexion provides conclusive evidence of rupture of the ACL. A detailed study of pathological displacement is the basis for a classification of laxity. It is then possible to decide for each type of laxity, the surgical treatment which is specifically adapted to the lesion, and to define a reference value for judging outcome.     

The clinical relevance of instrumented testing for ACL insufficiency. Experience with the UCLA clinical knee testing apparatus

An instrumented clinical testing device developed at UCLA records a continuous anteroposterior force versus displacement curve of the tibia with respect to the femur at 20 degrees of flexion. Laxity and stiffness are calculated from the response curve. With this device, 95% of normal knees have an anterior laxity less than 7.5 mm and a side-to-side difference less than 2 mm. In contrast, an anterior cruciate ligament (ACL) absent knee has a mean anterior laxity of 10 mm and a mean side-to-side difference of 5 mm. In a small group of patients with an intraarticular ACL substitution using the medial or lateral one-third of the patellar tendon, laxity and stiffness of the injured knees were returned to within the normal range and remained constant three years after surgery. In a group of 76 patients treated with ACL substitution using the torn meniscus, 51% of the patients still had an anterior laxity outside the normal range 3.5 years after surgery. In a preliminary study of 19 patients receiving a Gore-Tex synthetic ACL substitution, 55% of the patients still had a side-to-side difference greater than 2 mm two years after the procedure. These studies illustrate the advantages of impartial, objective measurements of knee stability. Laxity and stiffness values can supplement, but never replace, a thorough patient examination and patient history. As sports medicine matures as a scientific discipline, improved instrumented test devices may ultimately provide a standardized means for reporting knee stability parameters.     

Can suture repair of ACL transection restore normal anteroposterior laxity of the knee? An ex vivo study

Recent work has suggested the transected anterior cruciate ligament (ACL) can heal and support reasonable loads if repaired with sutures and a bioactive scaffold; however, use of a traditional suture configuration results in knees with increased anterior–posterior (AP) laxity. The objective was to determine whether one of five different suture repair constructs when performed at two different joint positions would restore normal AP knee laxity. AP laxity of the porcine knee at 60° of flexion was evaluated for five suture repair techniques. Femoral fixation for all repair techniques utilized a suture anchor. Primary repair was to either the tibial stump, one of three bony locations in the ACL footprint, or a hybrid bony fixation. All five repairs were tied with the knee in first 30° and then 60° of flexion for a total of 10 repair constructs. Suture repair to bony fixation points within the anterior half of the normal ACL footprint resulted in knee laxity values within 0.5 mm of the ACL‐intact joint when the sutures were tied with the knee at 60° flexion. Suture repair to the tibial stump, or with the knee at 30° of flexion, did not restore normal AP laxity of the knee. Three specific suture repair techniques for the transected porcine ACL restored the normal AP laxity of the knee at the time of surgery. Additional studies defining the changes in laxity with cyclic loading and in vivo healing are indicated. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1500–1505, 2008     

Factors for the presence of anteromedial rotatory instability of the knee

Anteromedial rotatory instability (AMRI) of the knee joint was investigated with an instrument newly designed to simulate the manual AMRI test and to quantify its magnitude. Thirty healthy subjects, 20 patients with anterior cruciate ligament (ACL) injury, and 10 with both ACL and medial collateral ligament (MCL) injuries were examined. Using the instrument, 100N of anterior force was applied to the proximal part of the tibia with the foot in neutral rotation, 30° of internal rotation, and 30° of external rotation, and the magnitude of anterior displacement was recorded. The measurement was carried out at 20° and 90° of flexion. A significant increase in anterior laxity was observed in all three rotation positions in the injured patients. However, the magnitude of laxity in external rotation was less than that in neutral rotation in the ACL injured patients, whereas it was the greatest in external rotation in ACL + MCL injured patients. Thus, we conclude that an injury involving both the ACL and MCL causes AMRI.     

The late course of acute partial anterior cruciate ligament tears. A nine to 15-year follow-up evaluation.

Twenty-two patients had an acute anterior cruciate ligament (ACL) tear. Nineteen patients were treated conservatively, except for associated injuries. In three patients, a reinsertion of the torn portion of the ACL was done surgically. All patients were reexamined after nine to 15 years with special emphasis on stability testing; this was done manually and with instruments. Knee function score and activity level were also measured. Standing roentgenograms with the knee in slight flexion were taken as well. At follow-up examination, none of the patients had needed ACL reconstruction. Knee function was good, with a mean Lysholm score of 93 points. Patients had changed activities from recreational team sports to light individual sports. Manual laxity values were similar to the values obtained at the time of initial injury. A 1-mm sagittal laxity increase was found on the injured knee with the Stryker laxity tester. Slight signs for osteoarthrosis were found in more than half of the knees, mainly in cases with chondral fractures or meniscectomy. In general, conservative treatment had a good long-term prognosis.     

In Vivo Gap Analysis in Various Knee Flexion Angles During Navigation-Assisted Total Knee Arthroplasty

Achieving rectangular flexion and extension gaps is important during gap balancing technique in total knee arthroplasty (TKA). However, assessment of gaps throughout the range of knee motion is obscure. One hundred knees operated by TKA using a navigation-assisted gap balancing technique were evaluated. Intraoperatively, after achieving rectangular flexion and extension gaps, mediolateral gaps in each flexion angle (0°, 45°, 90°, 120°) were recorded. Patients were divided into 4 groups; Group I: no gap difference (n = 64), Group II: lax in midflexion (n = 20), Group III: lax in deep flexion (n = 8) and Group IV: lax in both midflexion and deep flexion (n = 8). This study demonstrated that significant proportion (36%) of TKA cases had laxity in midflexion (45°) even when rectangular extension (0°)–flexion (90°) gap was achieved.     

Revision anterior cruciate ligament reconstruction using the lateral third of the ipsilateral patellar tendon after failure of a central-third graft: a preliminary report on 10 patients

Long-term outcomes were reported for 10 (77%) of 13 cases of revision anterior cruciate ligament (ACL) reconstruction using the lateral third of the ipsilateral patellar tendon as a graft. All primary ACL reconstructions were ipsilateral central-third bone-patellar tendon-bone graft procedures. Mean age at follow-up was 30.7 years, and mean time from revision ACL surgery to follow-up was 42.9 months. At follow-up, average KT-1000 difference between knees was 2.4 mm. All patients had a negative pivot shift, extension within 5 degrees of the contralateral knee, and flexion within 15 degrees. Mean bilateral comparison ratios for isokinetic strength and hop testing were: extension, 83.5%; flexion, 96%; and single-leg hop 96.9%. No patella fractures or tendon ruptures had occurred. All patients had returned to their previous work level, and 8 of the 10 patients could participate in at least "moderate" sports activities (e.g., skiing and tennis). The results were comparable to published outcome reports for both primary and revision ACL reconstruction. The lateral third of the ipsilateral patellar tendon is a good graft option for revision ACL reconstruction.     

The use of platelets to affect functional healing of an anterior cruciate ligament (ACL) autograft in a caprine ACL reconstruction model

Many anterior cruciate ligament (ACL) reconstructions have increased laxity postoperatively. We hypothesized that enhancing an ACL graft with a collagen‐platelet composite (CPC) would improve knee laxity and graft structural properties. We also hypothesized the platelet concentration in the CPC would affect these parameters. Twelve goats underwent ACL reconstruction with autologous patellar tendon graft. In six goats, a collagen‐platelet composite was placed around the graft (CPC group). In the remaining six goats, the collagen scaffold only was used (COLL group). Three goats were excluded due to complications. After 6 weeks in vivo, anterior–posterior (AP) laxity and tensile properties of the ACL reconstructed knees were measured and normalized against the contralateral intact knee. At a knee flexion angle of 30°, the average increase in AP laxity was 40% less in the CPC group than the COLL group (p = 0.045). At 60°, the AP laxity was 30% less in the CPC group, a difference that was close to statistical significance (p = 0.080). No differences were found between treatment groups with respect to the structural properties (p > 0.30). However, there were significant correlations between serum platelet concentration and AP laxity (R² = 0.643; p = 0.009), maximum load (R² = 0.691; p = 0.006), and graft stiffness (R² = 0.840; p < 0.001). In conclusion, use of a CPC to enhance healing of an allograft ACL reconstruction inversely correlated with early sagittal plane laxity and the systemic platelet count was highly predictive of ACL reconstruction graft strength and stiffness at 6 weeks. These findings emphasize the importance of further research on delineating the effect of platelets in treating of ACL injuries. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 631–638, 2009     

Early range of motion of the scorpio non-restrictive geometry cruciate-retaining total knee system

Flexion following total knee arthroplasty in the US population generally falls between 100° and 120°. Because of these relatively low flexion arcs, total knee arthroplasty prosthetic designs emerged allowing “high flexion” (≥125°). We hypothesized that a high-flexion implant design, Scorpio Non-Restrictive Geometry cruciate-retaining knee prosthesis, would allow clinical early maximum flexion of at least 125°. A prospective observational cohort study enrolled 87 unselected patients (94 knees) evaluated preoperation and 3 months and 1 year postoperation for clinical flexion, arc of motion, and Knee Society scores. At 1 year, 67% of knees had improved flexion and 23% achieved flexion of at least 125°. Clinically, flexion improved by 6.9° and total arc of motion improved by 10.6° from preoperation to 1-year postoperation. Although this high-flexion design allows increased flexion, many patients fail to achieve flexion of at least 125°.     

Quadrupled bone-semitendinosus ACL reconstruction: a prospective clinical investigation in 100 patients

Abstract The hypothesis of our study was that a quadrupled bonesemitendinosus tendon graft could combine the advantage of bone-tobone healing with the high cross-sectional area of a quadrupled hamstring graft in ACL reconstruction. ACL reconstruction with a semitendinosus tendon graft was performed on 100 patients with isolated ACL injury from January 1996 to December 1999: femoral fixation was obtained with Endobutton and tibial fixation with Fastlok. Patients were evaluated for standard knee scores and functional strength tests, postoperative pain rating, knee radiographs taken after surgery and at final follow-up, magnetic resonance images at 3 and 6 months, isokinetic flexion-extension and internal-external rotation tests at 3, 6, and 12 months. Computerized laxity analysis was performed at final evaluation. Average surgical time was 85 minutes, including 13 minutes for graft preparation; 90% of the patients were discharged within 24 h. Subjective knee rating was 80%; kneeling test was positive in 7% and Werner score was 44 (range, 30–48). Lachman test was negative in 90% at final evaluation (mean follow-up, 38 months). Sensory changes at the anterior part of the proximal tibia were present in 30% at 3 months and 10% had definite hyposthesia. MRI showed graft incorporation at 3 months. Computerized laxity analysis revealed 90% with less than 3-mm side-to-side differences. Isokinetic testing showed normal hamstring and quadriceps peak torques at 12 months. The functional strength tests were normal by 6 months. Average Noyes score was 87.9, Lysholm score 93, and Tegner activity rating 6.0 (pre-injury, 6.1). IKDC score showed 90 normal or nearly normal knees, 9 abnormal, and one severely abnormal knee. Quadrupled bone-semitendinosus is a viable graft for ACL reconstruction and should be considered, especially in patients with pre-existing extensor mechanism problems.     

Effect of tension and placement of a prosthetic anterior cruciate ligament on the anteroposterior laxity of the knee.

We wished to determine the optimal tension required to restore normal joint laxity to anterior cruciate ligament (ACL)-deficient knees using a braided polyethylene ACL prosthesis (PACL). In 10 cadaveric specimens, we measured the anteroposterior (AP) laxity of the intact knee at 10 degrees, 30 degrees, 60 degrees, and 90 degrees of flexion. The ACL was then removed and replaced with the PACL using tunnel-tunnel (T-T) and "over-the-top" (OTT) placement techniques. In both positions, the PACL was initially tensioned to 0, 9, 18, and 27 N with the knee flexed to 30 degrees. AP joint laxity was then measured at each flexion angle. With an increase in initial tension, there was a corresponding decrease in AP laxity. At 30 degrees and 90 degrees of flexion, AP laxity was not significantly different from normal using T-T placement and an initial tension of 0 N. At 90 degrees of flexion, AP laxity was not significantly different from normal using OTT placement at 0 or 9 N of initial tension. For both positions, all other tension levels and flexion angles constrained AP laxity. No laxity differences were detected between the OTT and T-T positions at any flexion angle. The variability in AP laxity of the T-T position was significantly greater than OTT. With a 150-N anterior shear force applied to the proximal tibia, the maximum tensions developed in the PACL were not significantly different between the two positions except at 90 degrees. The results suggest that implantation of the PACL is best performed using OTT positioning with an initial tension of 0 N applied at 30 degrees of knee flexion.     

Influence of collateral ligament laxity on patient satisfaction after total knee arthroplasty: a comparative bilateral study

Introduction Correct ligamentous balancing is an important determinant of the clinical outcome in total knee arthroplasty (TKA). Many surgeons prefer a tight rather than a lax knee during implantation of a TKA. The hypothesis in this study was that patients with a slightly laxer knee joint might perform better than patients with a tight knee joint after implantation of a TKA.Patients and methods Twenty-two patients with bilateral knee arthroplasties were clinically and radiologically evaluated at a mean follow-up of 4.5 years, ranging from 2 to 7 years. There were 12 women and 10 men with an average age of 68.9 years (range 32–82 years) at the time of surgery. A modified HSS score (excluding laxity), varus and valgus stress X-rays in 30° of knee flexion, and the subjective outcome of both knees were compared. A knee was considered tight when it opened less than 4° and lax if it opened 4° or more on stress X-ray.Results There was a trend towards improved range of motion and HSS score for the laxer knee joints. However, the difference did not achieve statistical significance. Eleven of the 22 patients considered one side subjectively better than the other side. In 10 out of these 11 TKA, the slacker knee joint was the preferred side (p<0.05).Conclusions As the present study compared bilateral knee joints after TKA, the same patient could act as a control group, and subtle subjective differences were revealed which are not quantifiable. The results showed that patients with a preferred side felt significantly more comfortable on the laxer side, indicating that during intraoperative ligamentous tensioning, some varus and valgus laxity at 20–30° of flexion might be preferable to an over-tight knee joint. Further biomechanical and prospective investigations will be necessary to establish the correct soft-tissue tensioning.     

Functional medical ligament balancing in total knee arthroplasty

Function of the anterior and posterior oblique portions of the medial collateral ligament and the posterior capsule in flexion and extension was evaluated in eight knee specimens after posterior cruciate retaining total knee arthroplasty. The posterior oblique portion of the medial collateral ligament was released subperiosteally in four specimens, and the anterior portion was released in four specimens. The medial posterior capsule was released in each group, then the remaining portion of the medial collateral ligament was released. Release of the posterior oblique portion produced moderate laxity at full extension and at 30 degrees flexion, and posterior capsule release produced additional laxity in full extension. Release of the anterior portion produced major laxity at 60 degrees and 90 degrees flexion. Complete medial collateral ligament release increased laxity significantly in both groups in flexion and extension. This rationale was tested in a clinical study of 82 knees (76 patients) in which 62 (76%) required medial collateral ligament release to correct varus deformity during posterior cruciate retaining total knee arthroplasty. Twenty-two knees (35.5%) were tight medially in extension only, and were corrected by releasing the posterior oblique portion. Thirty-one knees (50%) were tight medially in flexion only, and were corrected by releasing the anterior portion. Nine knees (14.5%) were tight medially in flexion and extension and required complete medial collateral ligament release, but three knees (4.8%) remained tight in extension and required medial posterior capsule release to correct flexion contracture and medial ligament contracture. Seventeen (27%) had partial posterior cruciate ligament release to correct excessive rollback of the femoral component on the tibial surface.