a Departamento de Ortopedia, Santa Casa de São Paulo, São Paulo, SP, Brasil
b Serviço de Ortopedia e Traumatologia, Hospital Israelita Albert Einstein, Universidade Federal de São Paulo (Unifesp), São Paulo, SP,Brasil
c Instituto de Ortopedia, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo (USP), São Paulo, SP, Brasil
d Escola Paulista de Medicina, Universidade Federal de São Paulo (Unifesp), São Paulo, SP, Brasil
Introduction
Injuries or tears to the anterior cruciate ligament (ACL) in ath-letes or physically active individuals are seen very often inorthopedic practice. Epidemiological studies have showed thatthe incidence is approximately 80,000 injuries per year.
1The first reports on ACL injuries appeared in the literaturein the nineteenth century.2Records of surgical reconstruc-tion first appeared at the beginning of the twentieth century.3Over the last 30 years, many surgical techniques have beendescribed for reconstructing this ligament, using several struc-tures as a graft source. A long path was followed until thetechnique described by Campbell4in 1939, which used thepatellar ligament, was returned to. Also in that year, Macey5described the first technique using the flexor tendons of thesemitendinosus and gracilis (ST-G).
Although the great advances in surgical techniques havereduced the time taken for patients undergoing ACL recon-struction to return to their activities,6we did not find anystudies in the literature correlating the angles of the tunnelswith the postoperative results.
There is no consensus regarding the various techniquesfor ACL reconstruction that have been described, in relationto comparisons between the postoperative results. There istherefore a need for better examination of the possible variablethat might correlate with a better final result.
Currently, tibial tunnels are constructed using prefabri-cated guides that are adjustable according to the angle thatis desired.
The objective of this study was to ascertain the coronalangle of the femoral and tibial tunnels that would providethe best postoperative result from ACL reconstruction surgery,using the following assessment criteria: patient's complaints,satisfaction with the result, Lysholm-Tegner questionnaire(Annex 1), IKDC questionnaire (Annex 2), clinical examinationand hopping on one foot.
Material
The knees of 16 patients were evaluated (Table 1). Thesepatients were seen at the knee surgery outpatient clinic ofthe Sobradinho Regional Hospital, Federal District, Brazil, andhad undergone ACL reconstruction performed by the samesurgeon, who was a specialist in knee surgeon.
The demographic characteristics (gender, age body massindex (BMI) and dominant leg) are listed in Table 1.
The inclusion criteria were as follows: a postoperativeperiod of between 24 and 48 months; ACL injury alone, asconfirmed by means of magnetic resonance imaging beforethe operation; physiotherapy applied after the operation; andhaving been released from rehabilitation (with or withoutreturning to the same activity level as before the injury).
The exclusion criteria comprised presence of any asso-ciated injuries to the ligaments, menisci or joint cartilage,revision surgery, inflammatory signs, neuromuscular dis-orders, infection, arthrofibrosis, lower-limb fractures, oradvanced osteoarthrosis in the femoropatellar or tibiofemoraljoints with evident displacement of the joint axis.
Table 2 details the factors correlated with the type of sportpracticed, the ground and the conditions under which theinjury and the rehabilitation took place.
All the patients underwent the same standard surgicaltechnique, consisting of grafting a single band from thesemitendinosus and gracilis tendons (ST-G) and use of a prox-imal crosspin fixation implant and an absorbable interferencescrew, with a distal cortical post (Fig. 1).
Method
The patients were given explanations regarding the aims ofthe study and, after agreeing to participate, they signed a freeand informed consent statement.
The present study was submitted to the research ethicscommittee of the Foundation for Health Sciences Teachingand Research (FEPECS) and was approved by this body underreport no. 0018/2010 and protocol no. 211/2010.
Non-sequential numbers were attributed to each knee thatunderwent surgery.
The clinical assessment was made firstly in a consultationoffice, where the patients' histories relating to the postopera-tive period were taken and the questions of the subjectiveInternational Knee Documentation Committee questionnaire(IKDC, 2000) and the Tegner-Lysholm Knee Scoring Scalewere applied and scores were attributed. The latter scale hasbeen validated for the Portuguese language.7Clinical exam-inations were performed in order to find out whether therewas any presence of joint effusion, crepitation, pain or lax-ity (Lachman, pivot-shift and anterior drawer tests), and kneegoniometry was performed. All these data were recorded on aspecific form (Annex 3).
The patients performed a hop test, from which a lower-limb symmetry index was obtained. This comprised the ratioof measurements of the distance jumped by means of a one-leg hop on the side that underwent surgery in comparison withthe non-operated side.
Lower-limb symmetry index = (distance with operatedlimb/distance with contralateral limb) × 100
The patients then underwent radiography (X-ray) of theoperated knee in anteroposterior (AP) view, in an uprightstanding position with weight-bearing in parallel and withparallel rays. The joint line tangential to the condyles and theaxes of the tunnels that had been constructed for the graftsto be inserted were traced out on these radiographs, and inthe coronal plane, and the angles in degrees were measured(Fig. 2).
Mean values were calculated from these angles and thepatients were then grouped into categories, according to theangles of the femoral and tibial tunnels on the AP knee radio-graphs (Table 3).
The postoperative results in terms of the following vari-ables were evaluated for each group, in relation to the tunneldata:
Patients' subjective satisfaction with the surgical result;
Scoring from the Lysholm-Tegner and IKDC questionnaires;
Limb symmetry index, with regard to the one-foot hop test.
Results
The mean angle of the tibial tunnels in the coronal plane (TTC)was 64.81?and that of the femoral tunnels (FTC) was 67.68?.The values measured at both sites were between 61 and 70?for most of the patients. The difference in alignment betweenthe tibial and femoral tunnels (TTC-FTC) is shown in Table 4.
The factors relating to the postoperative period and theevaluations according to the tests applied are shown in Table 5.
Group I (femoral tunnels = 65?and tibialtunnels in the coronal plane = 65?)
There were five individuals in this group (four men and onewoman). Their mean age was 29.6 years; the youngest was 22years of age and the oldest was 46.
This group included the patients with tibial and femoralangles that were the most horizontal in the coronal plane.
Both the femoral tunnels and the tibial tunnels had anglesof between 55?and 64?, with a mean of 61.2?for the femoraltunnels and 61?for the tibial tunnels. The difference betweenthe angles of the tibial and femoral axes ranged from varus of9?to valgus of 9?.
All of these patients had suffered injuries while practic-ing sports, each on a different type of ground surfacing. Oneof them said that he had not returned to sports activity anddeclared that he was dissatisfied with the result from thesurgery.
The mean IKDC score was 86.4 (range: 72-96) and the meanLysholm score was 94.4 (range: 85-100).
During the physical examination, two patients presentedpositive Lachman tests.In the hop test, the values ranged from 0.87 to 1 and themean limb symmetry index was 0.95.
Group II (femoral tunnels = 65?and tibialtunnels in the coronal plane > 65?)
The inclusion criteria for this group were fulfilled by only oneindividual: a 25-year-old male.
This patient presented a tibial angle that was more verticaland a femoral angle that was more horizontal, i.e. in principlesimilar to what is seen in the technique for constructing anarthroscopic transportal femoral tunnel.
The diaphysis-tunnel angle in the femur was 60?and in thetibia, 72?. The difference between the angles of the tibial andfemoral axes was a valgus angle of 12?.
This patient presented maximum scores in the IKDC andLysholm-Tegner questionnaires (100 and 97 points, respec-tively) and had negative Lachman, anterior drawer andpivot-shift tests in the physical examination. His limb sym-metry index was 1 in the hop test. This patient did not presentany spontaneous complaints when asked during the studyperiod. He declared that he was satisfied with the result fromthe surgery and he returned to physical activity eight weeksafter the operation.
Group III (femoral tunnels > 65?and tibialtunnels in the coronal plane = 65?)
There were five individuals in this group (four men and onewoman. The mean age of this group was 30.4 years: theyoungest was 23 years of age and the oldest was 40.
This group included patients with tibial angles that weremore horizontal and femoral angles that were more verticalin the coronal plane.
The angles formed by the axes of the diaphyses and tunnelswere, for the femur, between 68?and 70?(mean: 69.2?) and, forthe tibia, between 60?and 64?(mean: 61.8?). The differencebetween the angles of the femoral and tibial axes varied from-10?to -4?, i.e. always in varus.
All of the patients in this group had suffered injuries whilepracticing sports: three on synthetic grass and two on mats.
The scores from the IKDC questionnaire ranged from 85 to97, with a mean value of 91.2, and the scores from the Lysholmquestionnaire were from 88 to 100, with a mean of 93.4.
During the physical examination, one patient presentedpositive Lachman and pivot-shift tests. One individual statedthat he had not returned to sports activity, but he consideredhimself satisfied with the results from the surgery.
In the hop test, the mean value of the limb symmetry indexwas 0.94, with a minimum of 0.85 and a maximum of 1.
All of these patients stated that they were satisfied with thepostoperative results, although there were some spontaneouscomplaints such as pain while squatting, snaps and insecurityin performing jumps using the operated leg.
Group IV (femoral tunnels > 65?and tibialtunnels in the coronal plane > 65?)
There were five individuals in this group (four men and onewoman). Their mean age was 30 years: the youngest was 20years of age and the oldest was 45.
The angles formed between the axes of the diaphyses andtunnels among the patients in this group were the most verti-cal in the coronal plane. In the femur, the values ranged from70?to 82?(mean: 74.2?), while in the tibia they ranged from66?to 73?(mean: 70.2?). The difference between the angles ofthe femoral and tibial tunnels varied from -12?to + 3?, with amean of -4?(varus).
All of the patients in this group had suffered injuries whilepracticing sports: three on natural grass, one on a parquet floorand one on synthetic grass.
The scores from the IKDC questionnaire ranged from 89 to96, with a mean of 92.2, and the scores from the Lysholm ques-tionnaire ranged from 95 to 100, with a mean of 97.8 (Fig. 3).
During the physical examination, two patients presentedpositive Lachman and pivot-shift signs. One individual said
that he had not returned to sports activity, but he consideredhimself satisfied with the result from the surgery.
In the hop test, the mean value of the limb symmetry indexwas 0.99 with a minimum of 0.92 and maximum of 1.07 (Fig. 4).
There were spontaneous complaints with regard toincreased flexibility and paresthesia on the lateral face of theleg operated.
The means obtained from evaluating the study variablesare presented in Table 6.
Discussion
The present study was conducted with the aim of correlat-ing the angles of the bone tunnels with the postoperativeresults from ACL reconstruction. Some remarks need to bemade regarding the criteria that led to choosing this topic andin relation to the methodology used.
Studies on patients with ACL reconstructions that com-pared two types of graft, i.e. ST-G and the patellar tendon (PT),using the same fixation technique, have shown that there isno significant difference in anteriorization of the tibia. Thechoice between grafts therefore continues to be at the sur-geon's discretion.8This study did not aim to compare graftsources. Thus, only patients who underwent the techniquewith ST-G grafts were selected in the present study.
With regard to graft fixation, comparison between differentfixation methods was not our objective. The personal prefer-ence of the surgeon involved in this study, who has had greatexperience in such procedures, is to use a proximal crosspin with an absorbable interference screw and a distal post witha metal screw and washer.
The inclusion and exclusion criteria had the objective oflimiting the individuals studied to those who solely presenteda unilateral ACL injury, thereby eliminating the bias relatingto associated injuries. However, among the 300 patients whounderwent this surgery over the three-year study period, only26 fulfilled all the criteria and, of these, only 16 returned to theclinic for assessments for the present study.
The measurements of the tunnel angles were all made bythe same researcher, by means of simple radiographs. This isan inexpensive and widely available technique, but it gives riseto the possibility of variation of the angle measured accord-ing to the incidence of the rays. New studies using magneticresonance imaging might reduce or even eliminate this bias.
The patients were divided into groups according to themean values for the angles of the tunnels constructed. Thus,only one patient could be included in Group II. It was preciselythis individual who presented the best values for the post-operative results, among the variables studied. In the future,more patients could be included in new studies, in order toobtain a larger sample and ascertain whether these findingswould be maintained, and also whether significance would bereached with a more substantial number of individuals stud-ied.
Biomechanical studies on cadavers have shown that con-structing the femoral tunnel at an angle of 60?in the coronalplane minimizes the impact of the graft against the poste-rior cruciate ligament (PCL) and reduces the tension on thegraft under flexion. These studies have also shown that theloss of flexion and anterior laxity are greater when the tibialtunnel is drilled at an angle =75?in the coronal plane, andthat if the femoral tunnel is constructed more vertically viaan transtibial route (between 70?and 80?), there will be animpact against the PCL. These tunnels increase the tensionon the graft under flexion, which explains the limitation onflexion that is observed clinically. This impact against the PCLstretches the graft, which may explain the greater anteriorlaxity
It has been suggested from in vitro studies that, in orderto reduce the tension under flexion, the tibial tunnel shouldbe positioned at 60?in the coronal plane, because the angleof the femoral tunnel and the tension on the graft would becontrolled by this angle and this would improve the flexionand diminish the anterior laxity.
Thus, the enthusiasm for conducting new studies with theaim of finding the ideal angle for the tibial and femoral tunnelsis justified.
In the present study, it was observed that the groupsanalyzed presented differences in the outcome variablesaccording to the tunnel angles. Group I, in which the tunnelswere most horizontal (mean value for the tibial tunnel = 61?and for the femoral tunnel, 61.2?), had the lowest score forthe IKDC questionnaire (mean: 86.4) and the second lowestscore for the Lysholm questionnaire (mean = 94.4) and for thelimb symmetry (mean: 0.956). Group II, in which the tibial tun-nel was more vertical (72?) while the femoral tunnel remainedmore horizontal (60?), showed the best results and the valueswere the maximum possible for the IKDC, Lysholm and limbsymmetry index variables. Group III, in which the femoral tun-nel was more vertical (mean: 69.2?) while the tibial tunnel wasmore horizontal (61.8?), had the second worst IKDC (mean:91.2) and the worst values for the Lysholm variables (93.4) andfor the limb symmetry index (0.946). Group IV, in which thetibial tunnel (70.2?) and femoral tunnel (64.2?) were the mostvertical, showed the second best results for the three variables:Lysholm (97.8), IKDC (92.2) and limb symmetry index (0.996).
Conclusion
From the data obtained in the present study, it can be con-cluded that the results from groups II and IV were superiorto those from groups I and III. The two groups with the bestindices were the ones with the tibial tunnel more vertical. Thehighest scores from the IKDC, Lysholm and limb symmetryindex were obtained from a patient in whom the angles con-structed were 60?for the femoral tunnel and 72?for the tibialtunnel, which gave rise to a varus alignment for the tunnels.The worst results for the variables studied were found in thegroup in which the tibial tunnel was most horizontal and thealignment of the tunnels was most displaced toward valgus.Nonetheless, further studies are needed in order to confirmthese findings.
Conflicts of interest
The authors declare no conflicts of interest.
Annex 1. Lysholm questionnaire.
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