Variability in knee laxity in anterior cruciate ligament deficiency using a mechanized model

Purpose

To establish normative values for the magnitude of anterior tibial translation (ATT) in the Lachman and pivot shift tests in the intact and anterior cruciate ligament (ACL)-deficient states, and to explore whether a correlation in ATT magnitude exists between the Lachman and pivot shift tests.

Methods

Twenty-six fresh frozen cadaveric hip-to-toe specimens were used. Mechanized testing was performed to simulate both a Lachman and pivot shift test with the ACL intact. Tests were repeated after sectioning the ACL. ATT was recorded using a computer navigation system. Difference in ATT after sectioning was calculated for each specimen.

Results

For the Lachman, mean lateral compartment ATT in the intact knee was 5.3 mm (SD = 2.8 mm). After sectioning the ACL, translation increased to 11.4 mm (SD = 3.9 mm; P < 0.05). For the mechanized pivot shift, mean lateral compartment ATT in the intact knee was ?0.2 mm (SD = 2.6 mm). After sectioning the ACL, translation increased to 8.2 mm (SD = 3.1 mm; P < 0.05). No correlation in the magnitude of ATT was found between the intact and ACL-deficient knees for either the Lachman or pivot shift tests, or between both tests (Cronbach’s α < 0.7).

Conclusions

No correlation was found between the Lachman and pivot shift test in both the intact and ACL-deficient knee. This suggests that the Lachman cannot be used as a surrogate for the pivot shift as the magnitude of the Lachman did not predict the magnitude of the pivot shift.     

Effect of meniscal loss on knee stability after single-bundle anterior cruciate ligament reconstruction

Purpose

The menisci are known to be important secondary constraints to anterior translation of the tibia in the ACL-deficient knee. The effect of meniscal loss on knee stability as measured by the magnitude of the pivot shift following ACL reconstruction is unknown. The objective of this investigation was to determine the effect of meniscectomy on knee stability following two single-bundle ACL reconstruction strategies.

Materials and Methods

A mechanized pivot shift was performed on cadaveric specimens in the ACL-intact and ACL-deficient state. Tibiofemoral translation was recorded using a surgical navigation system. The ACL was reconstructed utilizing a nonanatomic graft (n = 10) extending from the posterolateral tibial footprint to the anteromedial femoral footprint, or an anatomic anteromedial single-bundle graft extending from the anteromedial tibial footprint to the anteromedial femoral footprint (n = 10) and testing repeated. The medial or lateral meniscus was sectioned and the examination repeated. The other meniscus was sectioned and the examination subsequently repeated.

Results

Lateral compartment translation during the pivot shift was significantly reduced following anatomic ACL reconstruction. In the nonanatomic group, lateral compartment translation increased by 9.1 mm (P < 0.001) after unicomparmental meniscectomy and 11.5 mm (P < 0.001) after bicompartmental meniscectomy. In the anatomic reconstruction group, lateral compartment translation increased by 7.6 mm (P < 0.001) after bicompartmental meniscectomy.

Conclusion

With isolated ACL injury, anatomic single-bundle ACL reconstruction controlled the pivot shift during time zero testing. However, significant increases in lateral compartment translation during the pivot shift are seen following bicompartmental meniscectomy. Nonanatomic ACL reconstruction was less effective in controlling the pivot shift at time zero testing, and significant increases in lateral compartment translation during the pivot shift were seen following both unicomparmental and bicompartmental meniscectomy.

     

What really happens during the Lachman test? A dynamic MRI analysis of tibiofemoral motion

BACKGROUND: The Lachman test is the most reliable clinical test for diagnosing rupture of the anterior cruciate ligament (ACL). It is generally believed that the lateral side contributes more than the medial side to anterior tibial translation, but this has never been convincingly proven. The MRI study presented in this article addresses this issue. HYPOTHESIS: The lateral side of the ACL-deficient knee contributes more than the medial side to anterior tibial translation. STUDY DESIGN: Prospective cohort study. METHODS: The Lachman test and the radiologic Lachman test were performed on 10 patients with isolated rupture of the ACL while the knee was scanned dynamically using open-access magnetic resonance imaging. The amount of movement in the midmedial and midlateral compartments of both the contralateral normal knee and the ACL-deficient knee was measured. RESULTS: In both normal and ACL-deficient knees, the lateral compartment contributes more than the medial to anterior translation of the tibia. Rupture of the ACL leads to increased laxity in both medial and lateral compartments with a statistically significant greater contribution from the lateral side. CONCLUSION: Rupture of the ACL leads to increased anterior tibial translation coupled with tibial internal rotation.     

Anteromedial versus central single-bundle graft position: which anatomic graft position to choose?

Purpose

To compare the time-zero stability of an anatomic anteromedial (AM) single-bundle ACL reconstruction to an anatomic central (CTR) single-bundle ACL reconstruction.

Methods

Twelve (6 paired) hip to knee cadaveric specimens were studied. Using custom ACL computer navigation software, a Lachman test and a previously validated, navigated mechanized pivot shift test were performed on 4 separate experimental groups in each specimen: (1) intact ACL, (2) ACL deficient with total medial and lateral meniscectomy, (3) following anatomic AM single-bundle ACL reconstruction, and (4) after anatomic CTR single-bundle ACL reconstruction. Maximum anterior tibial translation in each group was measured.

Results

Lachman: No significant difference was observed between the AM and CTR reconstructions (n.s.) or between reconstruction and the intact ACL (3.4?±?1.7?mm) (n.s.). Pivot Shift: Both the AM and CTR ACL reconstructions significantly reduced anterior translation relative to the ACL/menisci-deficient condition (lateral compartment: 8.9?±?3.8 mm and 6.75?±?4.6 mm vs. 17.25?±?3.5?mm, respectively; P?P?P?P?Conclusions It has been shown that there was no difference in the time-zero biomechanical stability between an anatomic anteromedial and anatomic central single-bundle ACL reconstruction. Given the current debate on the best anatomic ACL reconstruction technique, anatomic socket position in either the anteromedial or central locations provides similar time-zero biomechanics.     

Does a lateral plasty control coupled translation during antero-posterior stress in single-bundle ACL reconstruction? An in vivo study

The objective of this study was to quantify, in vivo, the reduction of knee laxity obtained by an extra-articular procedure, added to hamstring single-bundle (SB) anterior cruciate ligament (ACL) reconstruction in controlling coupled tibial translation during the Lachman and drawer tests. Twenty-eight patients were evaluated with a computer-assisted kinematic evaluation protocol; patients with associated ligament tears or meniscal damages were not included in the study. All patients underwent an hamstring ACL with an additional extra-articular procedure. During the intervention, tibia was tracked during the Lachman and drawer tests with ACL-deficient knee, after SB fixation and after extra-articular plasty fixation, performed with the remnant part of the hamstring tendons, from end of lateral condyle to Gerdy’s tubercle. Statistical analysis was performed to see whether there was a difference in knee laxity after the tests in the three steps. At 30°, the SB graft reduces AP translation of about 5 mm (P < 0.05) while the extra-articular procedure controls lateral tibial compartment, reducing translation by 1.6 mm (P < 0.05). At 90° the SB graft reduces AP translation more in the lateral compartment (P < 0.05), while the extra-articular procedure contributes in controlling tibial translation reducing laxity by 1 mm (P < 0.05) in both compartments. Result shows that, in vivo, the addition of an extra-articular procedure to single-bundle ACL reconstruction may be effective in controlling coupled tibial translation during the Lachman test and reduces AP laxity at 90° of flexion.     

Dynamic and static tibial translation in patients with anterior cruciate ligament deficiency initially treated with a structured rehabilitation protocol

Purpose

To compare dynamic and static tibial translation, in patients with anterior cruciate ligament deficiency, at 2- to 5-year follow-up, with the tibial translation after 4 months of rehabilitation initiated early after the injury. Secondarily, to compare tibial translation in the injured knee and non-injured knee and explore correlations between dynamic and static tibial translation.

Methods

Twelve patients with ACL rupture were assessed at 3–8 weeks after ACL injury, after 4 months of structured rehabilitation, and 2–5 years after ACL injury. Sagittal tibial translation was measured during the Lachman test (static translation) and during gait (dynamic translation) using a CA-4000 electrogoniometer.

Results

Static tibial translation was increased bilateral 2–5 years after ACL injury, whereas the dynamic tibial translation was unchanged. Tibial translation was greater in the injured knee compared with the non-injured knee (Lachman test 134 N 9.1 ± 1.0 vs. 7.0 ± 1.7 mm, P = 0.001, gait 5.6 ± 2.1 vs. 4.7 ± 1.8 mm, P = 0.011). There were no correlations between dynamic and static tibial translation.

Conclusion

Dynamic tibial translation was unchanged in spite of increased static tibial translation in the ACL-deficient knee at 2- to 5-year follow-up compared to directly after rehabilitation. Dynamic tibial translation did not correlate with the static tibial translation. A more normal gait kinematics may be maintained from completion of a rehabilitation programme to mid-term follow-up in patients with ACL deficiency treated with rehabilitation only.

Level of evidence

IV.

     

Knee laxity modifications after ACL rupture and surgical intra- and extra-articular reconstructions: intra-operative measures in reconstructed and healthy knees

Purpose

Quantifying the effects of anterior cruciate ligament (ACL) deficiency on knee joint laxity is fundamental for understanding the outcomes of its reconstruction techniques. The general aim of this study was to determine intra-operatively the main modifications in knee laxity before and after standard isolated intra-articular and additional extra-articular anterolateral reinforcement. Our main hypothesis was that laxity abnormalities, particularly axial rotation, can still result from these ACL reconstruction techniques.

Methods

Thirty-two patients with primary ACL deficiency were analysed by a navigation system immediately before and after each of the two reconstructions. Laxity measurements in terms of knee translations and rotations were taken during the anteroposterior drawer test, with internal–external rotation at 20° and 90° of flexion, and varus–valgus and pivot-shift tests. All these laxity measures were also taken originally from the contralateral healthy knee.

Results

With respect to the contralateral healthy knee, in the ACL-deficient knee significantly increased laxity (expressed in %) was found in the medial compared with that of the lateral compartment, respectively, 115 and 68 % in the drawer test at 20° flexion, and 55 and 46 % at 90° flexion. In the medial compartment, a significant 35 % increment was also observed for the coupled tibial anteroposterior translation during axial knee rotation at 20° of flexion. After isolated intra-articular reconstruction, normal values of anteroposterior laxity were found restored in the pivot-shift and drawer tests in the lateral compartment, but not fully in the medial compartment. After the reinforcement, laxity in the medial compartment was also found restored in the axial rotation test at 20° flexion.

Conclusion

In ACL reconstruction, with respect to the contralateral knee, intra-articular plus additional anterolateral reinforcement procedures do not restore normal joint laxity. This combined procedure over-constrained the lateral compartment, while excessive laxity still persists at the medial one.

Level of evidence

III.

     

Repair of the lateral posterior meniscal root improves stability in an ACL-deficient knee

Purpose

To investigate the stabilizing effect of a lateral meniscus posterior root repair in an ACL and root deficient knee.

Methods

The hypothesis of the current study was that a sequential transection of the posterior root and the meniscofemoral ligaments in an ACL-deficient knee increases rotational instability, and conversely, a repair of the meniscus root reduces the internal tibial rotation. Therefore, eight human knee joints were tested in a robotic setup (5 N m internal torque, 50 N m anterior translation load). Five conditions were tested: intact, ACL cut, ACL cut?+?lateral meniscus posterior root tear (LMRT), ACL cut?+?LMRT?+?transection of the MFL and ACL cut?+?lateral meniscus root repair. The angles of internal tibial rotation as well as anterior tibial translation were recorded.

Results

Transection of the lateral meniscus posterior root increased the internal tibial instability as compared to the ACL-insufficient state. A significant increase was detected in 60° and 90° of flextion. Sectioning of the meniscofemoral ligament further destabilized the knees significantly at all flexion angles as compared to the ACL-deficient state. Even in 30°, 60° and 90° a significant difference was detected as compared to the isolated root tear. A tibial fixation of the lateral meniscus root reduced the internal tibial rotation in all flexion angles and led to a significant decrease of internal tibial rotation in 30° and 90° as compared to the transection of the root and the MFL. The anterior tibial translation was increased in all conditions as compared to the native state.

Conclusion

A lateral meniscus root repair can reduce internal tibial rotation in the ACL-deficient knee. To check the condition of the lateral posterior meniscus root attachment is clinical relevant as a lateral meniscus root repair might improve rotational stability.

     

Sectioning the anterolateral ligament did not increase tibiofemoral translation or rotation in an ACL-deficient cadaveric model

Purpose

The anterolateral ligament (ALL) has been proposed as a possible extra-articular stabiliser of the knee. Injury to the ALL may result in residual instability following surgical reconstruction of a ruptured anterior cruciate ligament (ACL). Few studies have evaluated the biomechanical role of the ALL. The purpose of this study was to investigate whether sectioning the ALL would have an influence on tibiofemoral translation or rotation during the anterior drawer, Lachman, pivot shift, external rotation, and internal rotation tests in an ACL-deficient knee.

Methods

Only whole-body specimens having an ALL were included in this study. Lachman, anterior drawer, external rotation, and internal rotation tests were performed manually. Pivot shift test was done using a mechanised pivot shifter. The amount of tibiofemoral translation and rotation was recorded by a navigation system. Each specimen was tested in its native state, after sectioning the ACL, and after combined sectioning of the ACL and the ALL.

Results

In six out of 14 cadaveric knees, an ALL could be identified. The ACL-deficient knee had significantly more tibiofemoral translation and rotation compared to the native knee (P < 0.05). However, no changes in the magnitudes of translation or rotation were seen after subsequent sectioning of the ALL compared to the ACL-deficient knee (P > 0.05).

Conclusion

Adding an ALL lesion in an ACL-deficient knee did not increase tibiofemoral instability in this cadaveric model. It remains unclear whether injury to the ALL would result in substantial knee instability in the setting of ACL injury in vivo. Further research is warranted to fully elucidate the role of the ALL during knee kinematics and to determine in which scenarios ALL repair would be warranted. Understanding the function of the ALL may improve the current treatment strategies for ACL ruptures.

     

3-T MRI assessment of osteophyte formation in patients with unilateral anterior cruciate ligament injury and reconstruction

Objective

To define the number and distribution of osteophytes (OPs) in bilateral knee MRI (magnetic resonance imaging) of patients with unilateral anterior cruciate ligament (ACL) rupture.

Materials and methods

Bilateral knee MRIs of 20 patients with unilateral ACL rupture and reconstruction were retrospectively analyzed for OPs. OPs were graded following the KOSS (knee OA scoring system) classification and their compartmental distribution was assessed following the WORMS (Whole-Organ Magnetic Resonance Imaging Score) classification.

Results

All examined knees revealed OPs. Knees with ACL rupture showed significant (p?<?0.001) higher total numbers of OPs (mean 11.6; SD?±?4.4) than knees with intact ACL (mean 5.1; SD?±?2.3). Knees with ACL rupture showed increased OP formation in all knee compartments with predominance of marginal OPs in the lateral femorotibial compartment especially on the tibia.

Conclusions

Our results show that after knee injury with ACL rupture and reconstruction, all knee compartments were involved in post-traumatic increase of OP formation. The most affected compartment was the lateral femorotibial compartment on the tibial side.     

Combined ACL reconstruction and closing-wedge HTO for varus angulated ACL-deficient knees

Purpose

To report the medium-term clinical and radiographic outcomes of a group of patients who underwent anterior cruciate ligament (ACL) surgery combined with high tibial osteotomy (HTO) for varus-related early medial osteoarthritis (OA) and ACL deficiency knee.

Methods

Thirty-two patients underwent single-bundle over-the-top ACL reconstruction or revision surgery and a concomitant closing-wedge lateral HTO. The mean age at surgery was 40.1 ± 8.1 years. Evaluation at a mean of 6.5 ± 2.7 years of follow-up consisted of subjective and objective IKDC, Tegner Activity Level, EQ-5D, VAS for pain and AP laxity assessment with KT-1000 arthrometer. Limb alignment and OA changes were evaluated on radiographs.

Results

All scores significantly improved from pre-operative status to final follow-up. KT-1000 evaluation showed a mean side-to-side difference of 2.2 ± 1.0 mm. Two patients were considered as failures. The mean correction of the limb alignment was 5.6° ± 2.8°. Posterior tibial slope decreased at a mean of 1.2° ± 0.9°. At final follow-up, the mechanical axes crossed the medial–lateral length of tibial plateau at a mean of 56 ± 23 %, with only 1 patient (3 %) presenting severe varus alignment. OA progression was recorded only on the medial compartment (p = 0.0230), with severe medial OA in 22 % of the patients. No patients underwent osteotomy revision, ACL revision, UKA or TKA.

Conclusions

The described technique allowed patients with medial OA, varus alignment and chronic ACL deficiency to restore knee laxity, correct alignment and resume a recreational level of activity at 6.5 years of follow-up.

Level of evidence

Case series with no comparison group, Level IV.     

Influence of soft tissues on the proximal bony tibial slope measured with two-dimensional MRI

Purpose

Despite increasing interest in the functional anatomy of the menisci, little information is available regarding the relationship between the tibial slope and the menisci. It was hypothesized that the meniscus would reduce the differences in slope between the medial and lateral compartments and would mitigate the effects of age and gender on the tibial slope.

Methods

MRI sagittal images from 101 patients were used in this study. The angle between a line tangent to the medial and lateral tibial bony slope and the proximal tibial anatomical axis was measured on sagittal MRI images (bony slope). The angle between the tangent line to the highest point of the anterior and posterior horn of the meniscus and the proximal tibial anatomical axis was also determined (soft tissue slope). The measurements were carried out twice by two observers. The influence of gender and age on these parameters was analysed.

Results

Repeated measures analysis of variance showed good inter- and intra-observer reliability for both bony and soft tissue slope (ICC (0.87–0.93) and (0.91–0.97) for inter- and intra-observer reliability, respectively). In both compartments, the soft tissue significantly reduced the tibial slope towards the horizontal plane. In addition, the soft tissue slope was significantly more horizontal in the lateral compartment compared to the medial compartment (p < 0.01). These differences were not influenced by age or gender.

Conclusion

The menisci of the knee generate a more horizontal tibial slope when measured on MRI. The soft tissue slope is more horizontal in the lateral compartment of the knee compared to the medial compartment.

Level of evidence

Diagnostic, Level III.     

Roles of ACL remnants in knee stability

Purpose

This study evaluated knee laxity in anterior tibial translation and rotation following removal of anterior cruciate ligament (ACL) remnants using a computer navigation system.

Methods

This prospective study included 50 knees undergoing primary ACL reconstruction using a navigation system. ACL remnants were classified into four morphologic types: Type 1, bridging between the roof of the intercondylar notch and tibia; Type 2, bridging between the posterior cruciate ligament and tibia; Type 3, bridging between the anatomical insertions of the ACL on the lateral wall of the femoral condyle and the tibia; and Type 4, no bridging of ACL remnants. Anterior tibial translation and rotatory laxity were measured before and after remnant resection using a navigation system at 30°, 60°, and 90° of knee flexion. The amount of change in anterior tibial translation and rotatory laxity of each type was compared among the types.

Results

The different morphologic types of ACL remnants were as follows: Type 1, 15 knees; Type 2, 9 knees; Type 3, 6 knees; and Type 4, 20 knees. The amount of change in anterior tibial translation and rotatory laxity at 30° knee flexion in Type 3 was significantly larger than in the other types. There were no significant differences in either tibial translation or rotatory laxity at 60° and 90° knee flexion among the types.

Conclusions

In Type 3, ACL remnants contributed to anteroposterior and rotatory knee laxity evaluated at 30° knee flexion. The bridging point of the remnants is important to knee laxity. The Type 3 remnant should be preserved as much as possible when ACL reconstruction surgery is performed.

Level of evidence

Prognostic study, Level II.     

Female sex is associated with greater rotatory knee laxity in collegiate athletes

Purpose/hypothesis

The purpose of this observational study was to determine which factors, including sex, are associated with increased rotatory knee laxity in collegiate athletes with no history of knee injuries. It was hypothesized that increased rotatory knee laxity, measured by a quantitative pivot shift test, would correlate with female sex, increased anterior translation during the Lachman test, generalized ligamentous laxity, and knee hyperextension.

Methods

Ninety-eight collegiate athletes with a median age of 20 (range 18–25) years with no history of knee injuries were tested. IKDC and Marx activity scores were obtained and subjects underwent measurement of anterior translation during the Lachman test with a Rolimeter and measurement of knee hyperextension with a goniometer for both knees. A standardized pivot shift test was performed in both knees and quantified using image analysis technology. Generalized ligamentous laxity was assessed using the modified Beighton score.

Results

The average anterior translation of the lateral compartment during the pivot shift test was 1.6 mm (range 0.1–7.1) with a mean side-to-side difference of 0.6 mm (range 0–2.7). The average anterior translation during the Lachman test was 9.0 (range 2–15). The anterior translation of the lateral compartment during the pivot shift test was significantly higher in females (median, 1.6; range 0.3–4.9) than in males (1.1, 0.1–7.1 mm) (p < 0.05). Anterior translation of the lateral compartment during the pivot shift test was significantly correlated with anterior translation during the Lachman test (r = 0.34; p < 0.05). There was no significant correlation between anterior translation of the lateral compartment during the pivot shift test and knee hyperextension or modified Beighton score (n.s).

Conclusion

The data from this study show that female sex is associated with increased rotatory knee laxity measured during the pivot shift test and anterior translation during the Lachman test in collegiate athletes. In the future, these data may be helpful in diagnosing and managing ACL injuries in athletes and could be used in the clinic as a baseline by which to compare and identify patients who might exhibit increased rotatory laxity.

Level of evidence

Diagnostic level II.

     

Anatomic single- versus double-bundle ACL reconstruction: a meta-analysis

Purpose

To determine whether anatomic double-bundle anterior cruciate ligament (ACL) reconstruction compared to anatomic single-bundle ACL reconstruction more effectively restored antero–posterior (A–P) laxity, rotatory laxity and reduced frequency of graft rupture. Our hypothesis was that anatomic double-bundle ACL reconstruction results in superior rotational knee laxity and fewer graft ruptures due to its double-bundle tension pattern, compared with anatomic single-bundle ACL reconstruction.

Methods

An electronic search was performed using the PubMed, EMBASE and Cochrane Library databases. All therapeutic trials written in English reporting knee kinematic outcomes and graft rupture rates of primary anatomic double- versus single-bundle ACL reconstruction were included. Only clinical studies of levels I–II evidence were included. Data regarding kinematic tests were extracted and included pivot-shift test, Lachman test, anterior drawer test, KT-1000 measurements, A–P laxity measures using navigation and total internal–external (IRER) laxity measured using navigation, as well as graft failure frequency.

Results

A total of 7,154 studies were identified of which 15 papers (8 randomized controlled trials and 7 prospective cohort studies, n = 970 patients) met the eligibility criteria. Anatomic ACL double-bundle reconstruction demonstrated less anterior laxity using KT-1000 arthrometer with a standard mean difference (SMD) = 0.36 (95 % CI 0.214–0.513, p < 0.001) and less A–P laxity measured with navigation (SMD = 0.29 95 % CI 0.01–0.565, p = 0.042). Anatomic double-bundle ACL reconstruction did not lead to significant improvements in pivot-shift test, Lachman test, anterior drawer test, total IRER or graft failure rates compared to anatomic single-bundle ACL reconstruction.

Conclusion

Anatomic double-bundle ACL reconstruction is superior to anatomic single-bundle reconstruction in terms of restoration of knee kinematics, primarily A–P laxity. Whether these improvements of laxity result in long-term improvement of clinical meaningful outcomes remains uncertain.

Level of evidence

II.     

Experimental loss of menisci, cartilage and subchondral bone gradually increases anteroposterior knee laxity

Purpose

Anteroposterior knee stability is a relevant factor for the decision-making process of various surgical procedures. In degenerative joints when the implantation of unicompartimental prostheses or corrective osteotomies of the limb are planned, the integrity of the anteroposterior stability with an intact ACL has been regarded as a necessary prerequisite. We hypothesise that joint degeneration, however, may influence the anteroposterior knee laxity. Therefore, we set out to test this hypothesis simulating a progressively ‘degenerated’ joint in an experimental cadaveric setting.

Methods

Twelve intact transfemorally resected Thiel-fixated cadaver knee joints were divided into 2 groups for manipulation in the medial or lateral compartment. In each knee, we performed (1) unilateral total meniscectomy; (2) simulation of advanced osteoarthritis, by unilateral total cartilage debridement; (3) simulation of a unilateral tibial impression fracture, by resection of 5 mm of the tibial plateau; (4) transection of the ACL. The KT-1000 arthrometer was used to measure the extent of anteroposterior translation at 30° of knee flexion.

Results

The mean value for tibial anteroposterior translation before intervention was 3.2 mm (SD: ±0.8). The mean translation after each intervention was 4.6 mm (SD: ±0.9; +44%; n.s.) after meniscectomy, 5.9 mm (SD: ±1.5; +84%; P < 0.05) after cartilage debridement, 8 mm (SD: ±1.5; +150%; P < 0.01) after bone debridement, and finally 9.7 mm (SD: ±2.2; +203%; P < 0.05) after resection of the ACL. There were no significant differences between the medial and lateral compartment.

Conclusion

In absence of massive osteophytes or capsular shrinkage, rapid loss of meniscus, cartilage and particularly loss of subchondral bone may result in a massive increase in anteroposterior translation, mimicking a tear of the ACL. In such a situation, a false positive impression of a ligamentous injury may arise, and decision making is falsely directed away from totally or partially knee joint-preserving procedures. Therefore, in degenerate joints, clinical evaluation of anteroposterior stability should rather rely on the presence of a firm stop than an overall increased joint translation.     

Optimal measurement of clinical rotational test for evaluating anterior cruciate ligament insufficiency

Purpose

Rotational instability in ACL insufficient knee addresses the symptom or the abnormal motion which can be reproduced and subjectively evaluated in the clinical exam. Clinically available quantitative measurement for this instability has not been established due to mixed testing maneuvers and complex kinematics. The purpose was to measure knee kinematics during three manually performed rotational tests and to determine the optimal method to detect the abnormality in ACL deficient knees.

Method

Thirteen unilateral ACL deficient patients were tested by internal and external pure rotational stress tests and pivot shift test under anesthesia before scheduled ACL reconstructions. Rotation and coupled motion, i.e., tibial anteroposterior translation, were measured using an electromagnetic measurement system. Additionally, the acceleration of the tibial posterior translation during pivot shift test was calculated. The differences of these parameters between ACL intact and deficient knees were tested.

Results

Knee rotation is not different between ACL intact and deficient during both pure rotational stress test and pivot shift test. The coupled anterior tibial translation during pivot shift test was significantly different between ACL intact, 13.5?±?4.1?mm, and deficient knees, 23.1?±?4.4?mm, (P?<?0.01) as well as the acceleration of the tibial posterior translation (1.1?±?0.4?m/sec² in intact knees, 3.2?±?1.5?m/sec² in deficient knees; P?<?0.01). The coupled motion during pure rotational stress tests was similar regardless of ACL condition.

Conclusion

The rotational instability of the ACL deficiency was reproduced only by the pivot shift test and detected only by measuring the tibial anteroposterior translation and acceleration of the tibial posterior reduction. Level of evidence Diagnostic study, Level III.     

The role of the tibial slope in sustaining and treating anterior cruciate ligament injuries

Purpose

A steep tibial slope may contribute to anterior cruciate ligament (ACL)-injuries, a higher degree of instability in the case of ACL insufficiency, and recurrent instability after ACL reconstruction. A better understanding of the significance of the tibial slope could improve the development of ACL injury screening and prevention programmes, might serve as a basis for individually adapted rehabilitation programmes after ACL reconstruction and could clarify the role of slope-decreasing osteotomies in the treatment of ACL insufficiency. This article summarizes and discusses the current published literature on these topics.

Methods

A comprehensive review of the MEDLINE database was carried out to identify relevant articles using multiple different keywords (e.g. ‘tibial slope’, ‘anterior cruciate ligament’, ‘osteotomy’, and ‘knee instability’). The reference lists of the reviewed articles were searched for additional relevant articles.

Results

In cadaveric studies, an artificially increased tibial slope produced an anterior shift of the tibia relative to the femur. While mathematical models additionally demonstrated increased strain in the ACL, cadaveric studies have not confirmed these findings. There is some evidence that a steep tibial slope represents a risk factor for non-contact ACL injuries. MRI-based studies indicate that a steep slope of the lateral tibial plateau might specifically be responsible for this injury mechanism. The influence of the tibial slope on outcomes after ACL reconstruction and the role of slope-decreasing osteotomies in the treatment of ACL insufficiency remain unclear.

Conclusion

The role of the tibial slope in sustaining and treating ACL injuries is not well understood. Characterizing the tibial plateau surface with a single slope measurement represents an insufficient approximation of its three-dimensionality, and the biomechanical impact of the tibial slope likely is more complex than previously appreciated.

Level of evidence

IV.     

The effect of notchplasty in anterior cruciate ligament reconstruction: a biomechanical study in the porcine knee

Introduction

Notchplasty is frequently performed by many orthopaedic surgeons during anterior cruciate ligament (ACL) reconstruction. The effect of notchplasty on tunnel placement and knee biomechanics with ACL reconstruction is not known.

Methods

Twelve (n = 12) porcine knees were tested using a robotic testing system. Four knee states were compared: (1) intact ACL, (2) ACL-deficient, (3) anatomic single bundle (SB) ACL reconstruction and (4) anatomic SB ACL reconstruction with a 5-mm notchplasty. The graft was fixed at 60° of flexion (full extension of porcine knee is 30°) with an 80-N tension. The knees were subjected to two loading conditions: an 89-N anterior tibial load (ATT) and 4 Nm internal (IR) and external tibial (ER) rotational torques. The kinematics and in situ force obtained from the different knee conditions were compared.

Results

There were no significant differences between pre- and post-notchplasty in the ER at 30° and 60° of knee flexion (n.s.). However, a significant difference was found between pre- and post-notchplasty in ATT at 30° and 60° of flexion (p < 0.05). The in situ force in the anatomic SB reconstruction with notchplasty was significant lower than the intact and anatomic reconstructed ACL pre-notchplasty at 30°, 60° and 90° of knee flexion (p < 0.05). In response to the IR tibial torque, there were significant differences between pre- and post-notchplasty in IR at 60° (p < 0.05) of knee flexion.

Conclusion

Notchplasty had greater effect on anterior stability than rotational stability. This change in knee kinematics could be detrimental to a healing bone graft, ligamentization and could lead to failure of the reconstruction in early post-operative period.     

Biomechanics of high tibial osteotomy

Purpose

This paper is a review of the biomechanical principles that support limb realignment surgery via osteotomy around the knee, principally high (proximal) tibial osteotomy.

Methods

The basic biomechanical principles have been described, and the related literature examined for evidence to support the recommendations made.

Results

The forces on the knee when walking are shown to lead to most of the load acting through the medial compartment, the most frequent site of degeneration of the knee, due to the adduction moment that acts during the weight-acceptance phase. Realignment of the limb to move the mechanical axis to a desired point within the knee is described, and the resulting joint contact pressures in the medial and lateral compartments are shown to be higher in the less-congruent lateral articulation when the load passes through the centre of the knee. At the same time, there can be changes of the posterior slope of the tibial plateau, and a slope of ten degrees can induce a shearing force, which stretches the ACL, of 0.5 body weight when the knee force is 3 times body weight. The options regarding tibial or femoral or even double osteotomies are discussed in relation to medial–lateral slope of the joint line. Secondary effects such as alteration of collateral ligament tension or of the height of the patella are described.

Conclusion

Critical review of the publications supporting osteotomy surgery suggests that many of the accepted ‘rules’ have little scientific evidence to show that they represent the best practise for long-term preservation of the joint.