Anterior cruciate ligament (ACL) reconstruction is the main method of treatment of ruptured ACL in elite athletes. Noncontact ACL injuries are most common in athletes aged 15–40 years that practice sports involving sharp changes of the movement biomechanics: football, handball, rugby, volleyball, alpine skiing, etc. [1, 2]. Every year, about 3% of amateur athletes suffer ACL injuries. In the high performance sports realm, this figure can go up to 15% [2]. Women are two to eight times more likely to damage the ACL, a probable reason thereof being the differences in neuromuscular patterns in men and women during and after puberty [3, 4]. Studies have shown that 35% of elite athletes fail to achieve their previous level of performance within two years after injury [5]. In 2015, Federal clinical guidelines "Rehabilitation of Knee Capsular Ligaments Injuries (Surgical Treatment)" were published [6].

The rehabilitation includes four stages. Duration of the first (early postoperative) and second (late postoperative) stages is up to three to four months, that of the third stage (pre-training) is up to six months, fourth stage (training) — up to a year. Some authors have identified the following timeframes in the four main stages of rehabilitation of patients with ACL injury: early postoperative (1 week); late postoperative (2–4 weeks); functional (5–8 weeks); training and recovery (9–24 weeks) [7]. The program of post-ACL reconstruction rehabilitation [8] allows strength training in the training and recovery period (9–32 weeks) from the ninth week; such training involves use of cable (pulley) machines to load knee and hip joint during flexion and extension exercises. High-class athletes need more advanced exercises to restore muscle strength of quadriceps and hamstring muscles, and these exercises should not put the ACL autograft in danger. Currently, biomechanical exercising machines capable of providing biofeedback meet these requirements better than any other option.

Athletes need accelerated rehabilitation programs, since a long path back to loads common to competitions can translate into deterioration or loss of their professional skills. There are some general post-ACL reconstruction care trends adopted by the orthopedic community, but there is neither a standardized protocol nor an established timeframe for returning to the competition level training loads [9]. Therefore, the rehabilitation of athletes after ACL reconstruction is an urgent topic today.

This study aimed to design a comprehensive rehabilitation program for athletes after arthroscopic ACL reconstruction, develop the isokinetic exercising technique that relies on the TECNOBODY IsoMove biomechanical exercising machine and evaluate the effectiveness thereof.

METHODS

By design, this study was a prospective controlled nonrandomized study; it involved 64 athletes aged 17–31 years, all practicing sports that imply extreme locomotor activity; all had their ACL reconstructed. Gender-wise, we recruited 38 (59.4%) women (mean age 22 ± 4.2 years) and 26 (40.6%) men (mean age 26 ± 4.8 years). In all cases, the surgery took place less than a week after the athletes were diagnosed with ACL rupture. The ligament reconstruction materials were autografts of tendons of the semitendinosus and tender muscles, tendons of the long peroneal muscle.

The inclusion criteria were: age 16–40 years; first ever arthroscopic ACL reconstruction with/without partial resection of the meniscus, with/without arthroscopic meniscus suture.

The exclusion criteria were: age below 16 and over 40 years; arthroscopic interventions on adjacent and contralateral joints of the lower limbs; history of knee osteoarthritis; refusal to participate at any stage of rehabilitation.

The total duration of the study was 38 months (from October 2018 to November 2021).

We compared effectiveness of the designed comprehensive rehabilitation program and the one suggested by the Federal clinical guidelines "Rehabilitation of Knee Capsular Ligaments Injuries (Surgical Treatment)" (hereinafter referred to as the Recommendations) in the context of rehabilitation of athletes. The comparison necessitated division of the participants into two groups: treatment group (TG) of 30 individuals that were rehabilitated following the purpose-designed program, and control group (CG) of 34 athletes whose rehabilitation followed the Recommendations. 

The rehabilitation of all participating athletes was organized at the Federal Research and Clinical Center for Sports Medicine and Rehabilitation of the Federal Medical Biological Agency. The programs started 3–4 weeks post surgery, which is the II phase in the timeframe of the purpose-designed program. All participants attended the sessions 3 times a week.

The Recommendations program [6] is divided into four periods (tab. 1).

The comprehensive rehabilitation program designed in the context of this study has five phases (tab. 2). 

The comprehensive program of medical rehabilitation included isokinetic training on a machine providing biofeedback. Isokinetic training of muscles in the concentric mode delivered a significant improvement of the quadriceps and hamstring muscle strength (average and maximum torque at angular velocities of 30 and 60° per second) [10].  Biodex 3 System (Model 333–250; Biodex Medical Systems, Shirley; USA) was employed with the following parameters: angular velocity of 180° per second, three sets of 20 repetitions twice a week.

We have proposed a technique involving the TECNOBODY IsoMove biomechanical complex (fig. 1). Isokinetic exercises had the knee flexors and extensors loaded in the concentric mode, with the range of motion from 20 to 110° and angular velocity of 30° per second. The sessions took place twice a week; for the first two weeks, the number of repetitions was 10, then the routine changed to three sets of  repetitions for the first two weeks, then twice a week, three sets of 15 repetitions for the next 2 weeks, then three sets of 20 reps for two weeks and then a week with three sets of 20 repetitions.  The total number of sessions was 15. The movements started with extension of the knee joint. First, the healthy limb was trained, then the operated one. These training sessions began eight weeks post surgery.

Eight weeks post surgery, during the III phase of the rehabilitation, both groups had the following parameters/ indicators assessed: impairments in the support and locomotor functions; lower limbs load distribution symmetry (enabled by DIERS Motion 4D, fig. 2) in the gait analysis mode (pedogait) at the speed of 3 km/h. The repeated control examinations took place 15 weeks post surgery at the end of the isokinetic training program.

The stride cycle (SC) for each limb consists of two main phases, support phase and transfer phase.  The duration of the support phase is 58–61% of the SC, that of the transfer phase is 42–39%. The distinction is made between right and left SC, with the two constituting the act of walking [12, 13].  We evaluated CS phases of OL and HL and compared the respective results registered in the TG and the CG. The evaluated parameters were Stand time (%), which is the time the limb supports from the moment the toe is off the ground to the moment heel of the contralateral limb accepts the load; Swing-time (%), which is the time of transfer of the non-supporting limb; Single limb support (%); Load sensitivity (%); Pre-swing (%), which is the time from resting on the toe to bouncing off (fig. 3). The first three parameters were statistically significant for the comparison. 

Statistical processing of the results was done manually in Microsoft Excel and Statistica for Windows v. 5.1.  To establish significance of the differences we used Student's t-test. The differences (t) were considered statistically significant at p ˂ 0.05.

RESULTS

The following criteria were chosen for an objective assessment of effectiveness of the programs compared: pain assessment on a visual analogue scale (VAS), range of motion, zigzag jump test, stride parameters in gait analysis.

The participants took the jump test 15 weeks after surgery. In the TG, less than 75% symmetry between limbs during the jump was seen in two athletes (6.7%), while in the CG it was registered in nine athletes (26.5%).

In the TG group, four athletes (13.3%) reported pain of 4 VAS points and one (3.3%) — 5 VAS points;  in the CG, seven participants (20.6%) put the pain sensation at 4 VAS points and two (5.9%) at 3 VAS points. Three months later, only one athlete (3.3%) reported pain of 2 VAS points in the TG, and in the CG the respective number of participants was 3 (8.8%).

A month later, the recorded active flexion radius in both groups was 100–110°, and passive flexion ranged up to 115– 130°. One athlete from the TG had active extension limited to 7° and passive extension to 3°. After months later, no contractures were registered in any of the groups.

Stability tests (Lachman drawer test, pivot shift test) performed 15 weeks later revealed no positive symptoms in any of the TG athletes. In the CG, these tests allowed registering a slight anterior translation of the lower leg with a clear final point.

Table 3 (tab. 3) shows the results of assessment of violations of the support and locomotor functions, lower limbs load distribution as registered with the DIERS Motion 4D complex.

Eight weeks after surgery, there were no significant differences found between groups in the parameters of support and locomotor functions violations as registered and analyzed with the DIERS Motion 4D complex. However, fifteen weeks after the reconstruction, when the TG members were through all the isokinetic training sessions, the results were as follows: for the Stand Time parameter, the OL support deficit was 0.04% compared to the HL support, and for the Single limb support parameter it was 3.71%, while in the CG the values were 12.44% and 18.55%, respectively. As for the Swing Time parameter, TG participants showed the deficit of HL transfer symmetry (relative to OL) of 3.99%, while the value of this parameter in the CG was 20.54%.

DISCUSSION

The results of the gait parameter analysis for the TG participants indicate a more effective recovery of muscle strength of the knee joint stabilizers, healing of disorders of the support and locomotor functions in the postoperative period that included isokinetic training, which implies resistance when a certain angular velocity is reached, translating into load for exercised muscles. These findings are consistent with those reported by other authors earlier [9, 10]. Therefore, the resistance that the athlete has to overcome is adaptable, it changes constantly in proportion to the effort exerted. As a result, the process of muscle strength recovery gain in effectiveness.

CONCLUSIONS

1. The designed comprehensive post-ACL reconstruction medical rehabilitation program for elite athletes has proven to be effective in restoring the knee joint stabilizer strength, healing of the support and locomotor function disorders, poor symmetry in the distribution of load on lower limbs. 2. The use of equipment providing biofeedback for rehabilitation of athletes allows speeding this process up and thus have the athletes recover their competition level capabilities sooner. 3. It is necessary to continue the search for the most effective isokinetic training technique relying on the TECNOBODY IsoMove biomechanical complex.