Proprioceptive training after ACL reconstruction: Standard versus stump preservation technique

Abstract

BACKGROUND:

Anterior cruciate ligament (ACL) injuries are considered to be among the most disabling knee injuries. The proprioception function affected due to ACL injuries results in functional instability as neuromuscular control is altered in consequence.

PURPOSE:

To compare proprioceptive training outcomes following ACL reconstruction with and without stump removal.

METHODS:

Thirty male patients received a three months rehabilitation program, including an integral proprioceptive training component, after having autogenous hamstring tendon ACL reconstruction. Fifteen patients had done stump shaving technique (group A), and fifteen patients with stump preservation (group B). Mean age was (32.87±7.51 years) for group A and (31.53±6.46 years) for group B. Clinical evaluation included functional performance measured by Lysholm scale, dynamic balance measured by Biodex balance system test (overall stability index), and sense of position measured by active and passive repositioning tests (absolute angular error) on Biodex system 3 isokinetic dynamometer.

RESULTS:

No significant differences were detected for active and passive repositioning tests and overall stability index of affected and non-affected legs between groups. Moreover, Lyshlom scores between both groups revealed no significant difference. Pairwise comparisons of affected and non-affected legs within either groups were also non- significant (p < 0.05).

CONCLUSION:

Proprioceptive training after arthroscopic ACL reconstruction showed similar effects on function, dynamic balance, and sense of position in patients operated by stump shaving or preservation techniques.

Keywords

ACL reconstruction proprioceptive training balance residual stump joint position sense

1 Introduction

Proprioception is a sensory modality that provides somatosensory information to the central nervous system about joint position and mobility, which controls tension of the muscles around the knee and react to those changes according to these information [1]. At the instances where joint positions are likely to exceed the boundaries of tissue safety, the muscle groups that provide dynamic protection to the knee reflexively become active to counteract the injuring force. For instance, hamstrings are activated to resist anterior tibial translation beneath the femur [2].

Knee proprioceptors play a fundamental role restoring high level of functional performance and achieving high patients’ satisfaction standards after ACL reconstruction surgeries. Accordingly, the outcomes of ACL reconstruction is likely depend on the restoration of effective proprioception function rather than the mechanical restraint of a graft [3, 4]. Mechanoreceptors serving proprioception are present in the ACL remnants, and may contribute to proprioception enhancement following reconstruction. Besides, enhancing proprioception function through reinnervation of the graft, remnant preservation ACL surgeries showed experimentally that they helps revascularization and ligamentization of the graft [5]. The more the mechanoreceptors in the remnants the better the proprioception even prior to reconstruction surgery [6]. Proprioceptors exist in ACL remnants following injury remain detectable for various length of time [7, 8]. While Denti et al. [7] reported that proprioceptors existed in remnants of injured ACL few months following injury, Georgoulis et al. [8] found proprioceptors in ACL remnants even as long as 3 years following injury. Furthermore, Ochi et al. [9] supported the likely viability of proprioceptors in ACL remnants; They were able to detect reproducible cortical somatosensory evoked potentials through stimulating ACL remnants in 15 out of 32 specimens.

Ihara and Nakayama [10] considered proprioception training to be a beneficial mean of facilitating sensorimotor control function through reducing the time between sensory input (proprioception) and motor response (muscle contraction). It was concluded that combining an accelerated rehabilitation program with an integral proprioception training component after ACL reconstruction is important to improve knee function [11].

This study aimed to compare the outcomes, knee function, balance, and joint position sense, of rehabilitation program with an integral proprioception component following ACL reconstruction with and without residual stump preservation. Although shaving of the residual stump is an easier and shorter surgical technique due to better visualization and hence better performance, it was hypothesized that, preserved residual ACL stumps would provide significantly better postoperative functional outcomes.

2 Material and methods

The current study was conducted at the outpatient clinics of the Faculty of Physical Therapy, Cairo University from June 2016 until September 2017. Orthopedic Surgery Department, Qasr Eleni Hospital, and Department of Orthopedic Physical Therapy at faculty of physical therapy, Cairo University approved the study on December 2015.

Thirty male patients with knee autogenous hamstring tendon ACL reconstruction participated in this study. One orthopedic surgeon performed surgeries for all study participants. Patients were randomized by block randomization method into 2 groups: group A (15 patients, with mean age of 32.87±7.51 years; mass 85.6±9.86 kg; height 180.87±9.17 cm) in which ACL was reconstructed with an ordinary method, ligament remnants were shaved off before graft insertion. Group B (15 patients, with mean age of 31.53±6.46; mass 82.53±10.37 kg; height 177.8±8.98 cm) in which ACL was reconstructed preserving the tibial remnant stump. Every patient signed a consent form. Patients were excluded from the study if their age exceeded 49 years or they had any of the following conditions: previous knee surgery, inflammatory arthritis, osteochondral diseases, previous knee injuries or fractures, association of PCL or knee collateral ligaments injuries.

2.1 Rehabilitation program

All patients in both groups received three training sessions per week of the same rehabilitation program, including proprioceptive training. The rehabilitation program was as follows:

2.1.1 Second week postoperatively

Full hyperextension was achieved by heel prop, prone hang and hamstring stretching exercises. Flexion to 110 degrees was accomplished through wall slide, heel slide, hamstring curl, and multiple-angle hamstring isometric exercises. Quadriceps muscle leg control was enhanced by quadriceps setting, straight leg raising (SLR), short-arc quadriceps exercise, and quadriceps isometrics with the knee at 90 degrees.

2.1.2 Weeks 3–6 postoperatively

Full knee range of motion was achieved with continued heel slide, stationary bicycle and kneeling stretch. Muscle strength was enhanced by resisted SLR, resisted short-arc quadriceps, and resisted hamstring curl exercises. Closed kinetic chain exercises included self-assisted step-up, double-legged mini squat, double leg press, and double-legged calf raise exercise.

2.1.3 Weeks 6–12 postoperatively

All the previous exercises were continued in addition to step-up exercise, single-legged mini squat exercise, single leg press exercise, single-legged calf raise exercise, exercise on a stationary bicycle, light jogging program, and agility training

2.2 Proprioceptive training program

All subjects received a proprioceptive training program on the Biodex balance system starting third week postoperative.

2.3 Double-leg stance (sessions 1 to 8)

Training started first with double leg stance (8 sessions). Stability level of the foot platform started at level 8 (most stable), and progressed one level each session until reaching level 1 in the 8th session. Patient stood on the foot platform with hands off-the support handle. Patient was trained for 10 minutes, 4 trials of 2.5 minutes with rest (1 minute) in between each of them, with open eyes trying to keep the cursor on the feedback screen directly in the middle. Patient then had 3 minutes rest before training for another 10 minutes, 4 trials of 2.5 minutes with 1 minute rest in between each of them, with closed eyes. During closed eyes trials patients tried to maintain the foot platform centered without visual feedback. Throughout all trials patients tried to maintain balance against the multidirectional tilting movement of the foot platform.

2.4 Single-leg stance (sessions 9 to 32)

Patient stood on the center of the foot platform on one foot; beginning with the non-affected side with hands off the support handle. Stability level of the foot platform was readjusted at level 8 (most stable), and progressed one level each week (3 sessions) till reaching level 1 in the last 3 sessions. Patient was allowed 2.5 minutes to train each leg alternately twice per session i.e. a total of 10 minutes, 4 trials of 2.5 minutes with rest 1 minute in between each of them, with open eyes trying to keep the cursor directly in the middle of the screen. The patient took 3 minutes rest before training with closed eyes. This was followed by another 10 minutes training in the same manner, 4 trials of 2.5 minutes with rest 1 minute in between each of them, with closed eyes. During closed eyes trials patients tried to maintain the foot platform centered without visual feedback. Throughout all trials patients tried to maintain balance against the multidirectional tilting movement of the foot platform.

2.5 Clinical evaluation after 3 months included

2.5.1 Functional performance

Subjective assessment of the knee was done in both groups at the end of the treatment using the validated functional scoring scale of Lysholm. The eight items scale; limping, weight bearing, locking, instability, pain, swelling, stair climbing, and squatting is used to assess common symptoms and restrictions of function in patients with knee ligamentous injuries on activities of daily living. Scores less than 68 were rated poor, from 68 to 77 were rated fair, then 78 up to 90 were rated good, and more than 90 to the top score of 100 were rated excellent [12].

2.5.2 Dynamic balance

Assessment of the patient’s neuromuscular control ability in a closed chain multiple directions test was applied using Biodex balance system. The test examined single leg dynamic balance on an unstable surface. Patient attempted to control a tilting platform and the degree of platform tilt was averaged over test time giving the outcome measure; overall stability index (OSI). A large variance was indicative of poor neuromuscular response [13, 14]. Firstly, tested patient received verbal explanation about the testing steps. The patient assumed the test position, standing on affected or non-affected feet without footwear, with arms held at both sides. The order of legs testing was randomized for each patient. Then patient centered himself on the foot platform before starting the test. Patient tried to control the deviation of the device platform as much as possible during the test. All patients were tested on stability level four. Three test trials, of 30 seconds each, for each leg with 1-min rest period between trials for each leg, and 3 minutes between legs. Average of the three trials was calculated for each foot [15].

2.5.3 Position sense

Patients assessed knee joint position sense using knee joint reposition tests on Biodex system 3 isokinetic dynamometer (Biodex Medical Systems, Shirley, New York, USA). Steps of measurement were explained for each patient, followed by entering personal data to computer database. Patients sat on Biodex isokinetic dynamometer with hips and knees flexed 90° and were blind-folded for the task. During familiarization and test trials the examiner stabilized the tested leg to the limb support pad of the knee attachment, making sure that the knee axis was aligned to the dynamometer axis, and the limb support pad 3 cm proximal to uppermost part of the lateral malleolus. Following which, the examiner set up the starting position to 90° knee flexion and the target position to 30° knee flexion. The patient moved the knee attachment actively to the target position, where the dynamometer held the target position for 5 seconds. The leg is then released and the patient returned to the starting position. In active repositioning trials, therapist asked the patient to move the knee attachment actively to where he felt the target angle was, then, to press the hold button. In passive repositioning the dynamometer passively moved from flexion towards extension, at preset angular velocity of 5°/second. The patient pressed the hold button where he felt he reached the target angle [16]. Before test trials for each test, patient performed 3 trial to be familiarized with the target position. Patients completed 3 test trials each leg in each test. The dynamometer software recorded absolute angular error (AAE), the absolute difference between actual leg position and target position in degrees, for each trial. The mean of the 3 test trials for each test was recorded and used for analysis [17].

2.6 Statistical analysis

Statistical analysis was performed using SPSS computer program (version 19 windows) (IBM Inc., Chicago, IL, USA). Results are expressed as mean±standard deviation. Shapiro-Wilk test of normality was conducted. Accordingly, comparison between normally distributed data was performed using unpaired t-test while comparison between non- normally distributed data was performed using Mann Whitney test for between groups and Wilcoxon signed ranks test for within groups comparisons. P value < 0.05 was considered significant.

3 Results

Demographic data of patients in the two groups showed non-significant differences between patients’ ages, mass, height, BMI, and time before surgery (Table 1). Regarding group A, nine left knees and six right knees were operated, while group B had 3 left knees and 12 left knees operated.

The results of comparison between all outcomes from the three dependent parameters, Lysholm knee scale, balance assessment (OSI), and assessment of joint position sense (AAE), compared between patients in both groups are shown in (Table 2).

Table 1
Demographic data in the two studied groups

Group A (n = 15) Mean (±SD) Group B (n = 15) Mean (±SD) Statistics P value

Age (yrs.) 32.87±7.51 31.53±6.46 t^* = 0.521 0.606

Mass (kg) 85.6±9.87 82.53±10.37 t^* = 0.830 0.414

Height (cm) 180.87±9.18 177.8±8.99 t^* = 0.925 0.363

BMI 26.33±3.71 26.1±2.75 t^* = 0.189 0.852

Time before surgery (days) 60.0 30.0 Z^# = –1.288 0.198

	Group A (n = 15) Mean (±SD)	Group B (n = 15) Mean (±SD)	Statistics	P value
Age (yrs.)	32.87±7.51	31.53±6.46	t^* = 0.521	0.606
Mass (kg)	85.6±9.87	82.53±10.37	t^* = 0.830	0.414
Height (cm)	180.87±9.18	177.8±8.99	t^* = 0.925	0.363
BMI	26.33±3.71	26.1±2.75	t^* = 0.189	0.852
Time before surgery (days)	60.0	30.0	Z^# = –1.288	0.198

P < 0.05; ^*t = Unpaired t- test; ^#Z = Mann Whitney test.

Table 2

Comparison between the dependent variables in the two studied groups

	Group A (n = 15) Mean (±SD)	Group B (n = 15) Mean (±SD)	Statistics	P value
Lysholm score	89.80±6.24	90.60±4.91	t^* = –0.390	0.699
Balance (OSI)
Affected	3.06±0.85	2.75±1.28	t^* = 0.773	0.446
Non affected	3.33±1.48	2.61±1.05	Z^# = –1.393	0.169
Joint position sense
Affected
Active	2.72±1.04	2.21±0.93	t^* = 1.428	0.164
Passive	2.26±1.99	2.38±1.13	t^* = –0.203	0.841
Non affected
Active	2.23±0.68	2.05±0.86	z^# = –1.065	0.148
Passive	1.66±0.83	2.17±1.12	Z^# = –1.022	0.158

P < 0.05; t^* = Unpaired t- test; Z^# = Mann Whitney test.

Since all non-affected legs measures in both groups were non-normally distributed, inter-side differences in patients within both groups were tested using Wilcoxon signed ranks test. Non-significant differences were detected in overall stability index, active and passive repositioning AAE (Table 3).

Table 3

Comparison between inter-side differences in balance and sense of position within both groups

	Affected legs Mean (± SD)	Non affected legs Mean (± SD)	statistics	P value
Balance (OSI)
Group A	3.06±0.85	3.33±1.48	Z^∧ = –1.050	0.313
Group B	2.75±1.28	2.61±1.05	Z^∧ = –0.399	0.708
Joint position sense
Group A
Active	2.72±1.04	2.23±0.68	Z^∧ = –1.614	0.115
Passive	2.26±1.99	1.66±0.83	Z^∧ = –1.021	0.336
Group B
Active	2.21±0.93	2.05±0.86	Z^∧ = –0.771	0.464
Passive	2.38±1.13	2.17±1.12	Z^∧ = –1.195	0.245

P < 0.05; Z^∧ = Wilcoxon signed ranks test.

4 Discussion

The present study investigated the difference between outcomes of rehabilitation program with an integral proprioception training following two different techniques of ACL reconstruction surgeries (standard ACL group versus remnant preserving group). The results showed non-significant differences between both groups regarding functional performance, dynamic balance, and sense of position.

This research finding is in agreement with Hong et al. [18] who found that the graft of both techniques of surgery have good clinical results. They detected no significant difference in between patients operated using both techniques in Lysholm score and joint position sense. In another study by Gohil et al. [19] and in spite of the improvement of vascularization in the remnant preservation group, no clinical differences were found between both techniques of surgery concerning functional outcomes as assessed using the score developed by international knee documentation committee (IKDC). Moreover, the current results come in agreement with Tie et al. [20] as they reported non-significant differences between the two techniques in functional outcome scores using both IKDC score and Lysholm score.

Controversial opinions have been published regarding the remnant-preserving anterior cruciate ligament surgery. While some studies [21 –24] reported an expected better healing and knee function following the remnant-preservation of ACL as this might enhance graft revascularization, proprioception, synovial coverage and the healing process. Furthermore, in a previous study the preserved remnant had significantly enhanced the graft collagen fibers reorientation, yield load, ultimate failure load and stiffness [25]. Based on these findings, they recommended this technique in ACL reconstruction surgery. On the contrary, other studies didn’t recommend the techniques, claiming a high risk for impingement and cyclops formation [5]. Besides, it showed no better post-operative stability, function or faster graft incorporation than standard shaving technique [26, 27].

The disagreement between the results of the current study and previous studies [21 , 28] that suggested enhanced function and/or proprioception following remnant preserving ACL reconstruction might have different reasons. Firstly, some studies [21, 22] reported their outcomes over a long follow up period ranging between 2 years and 50 months postoperatively compared to this study. Besides, their reports did not show the rehabilitation programs following reconstruction. Another source of difference might be the size of the remnant part. Lee et al. [28] reported better outcomes in the group with more than 20% of the native ACL preserved remnant as compared to those with 20% less remnant. In this study, the size of ACL remnants had not been accounted for, accordingly it is not possible to support or disagree with the previous finding. The different findings may also be attributed to the different knee joint structures, as some of those studies supporting the healing of graft and better function and proprioception were performed in animals, making differences between theoretical and laboratory findings [25, 29]. It is also important to consider the difference in rehabilitation program adopted after surgery, which may be another cause of different outcomes.

The comparison between affected and non-affected legs showed non-significant difference in balance and proprioception in both groups. These results probably indicate that the rehabilitation program adopted in the study with integral proprioception component worked to restore normal proprioception function following reconstruction in both types of surgery, within the 3 months’ timeframe. These results come in agreement with previous work [30] assessing knee proprioception between operated and normal knees 3 months postoperative and reporting no significant differences. Likewise, improvement of operated compared to contralateral knees post reconstruction were detected when comparing joint position sense and threshold to detection of passive movement [31]. Further, in that study both operated and contralateral knees proprioception reaching non- statistical difference with matched controls at 6 months follow-up. In another study [32] authors applied accelerated rehabilitation following ACL reconstruction and reported improve passive joint position sense over 6 months. However, they reported that the fast recovery of passive joint position sense occurred 3 months postoperatively in affected compared to preoperative values, then, rate of improvement was much slower. In the current study, it is applicable to suggest that proprioception training included in the rehabilitation program had normalized proprioception as there were no significant differences between active and passive joint position test absolute angular errors and overall balance index between affected and unaffected regardless of the surgical technique. Unfortunately, it is unlikely to quantify within groups improvement in proprioception function from preoperative stage till postoperative assessment as no preoperative data were collected from participating patients in either groups.

The research results are limited to the adopted program of rehabilitation and the measured parameters. Further studies are needed considering more sample number and long term effects. Further studies are also recommended comparing the different outcomes regarding different percentage of remnant preserving and various graft procedures.

In conclusion proprioceptive training after arthroscopic ACL reconstruction showed similar effects on function, dynamic balance, and sense of position regardless of stump removal or preservation. Short-term results were only reported and long term functional effects of the remnant-preserving technique still require to be investigated.

Conflict of interest

None to report.

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