Knee Surg Sports Traumatol Arthrosc DOI 10.1007/s00167-014-3261-5

Knee

Predictive parameters for return to pre‑injury level of sport 6 months following anterior cruciate ligament reconstruction surgery Ulrike Müller · Michael Krüger‑Franke · Michael Schmidt · Bernd Rosemeyer 

Received: 24 October 2013 / Accepted: 21 August 2014 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2014

Abstract  Purpose  The aim of the study was to find predictive parameters for a successful resumption of pre-injury level of sport 6 months post anterior cruciate ligament (ACL) reconstruction. Methods  In a prospective study, 40 patients with a ruptured ACL were surgically treated with semitendinosus tendon autograft. Six months after surgery, strength of knee extensors and flexors, four single-leg hop tests, Anterior Cruciate Ligament–Return to Sport after Injury Scale (ACL–RSI), subjective International Knee Documentation Committee (IKDC) 2000 and the Tampa Scale of Kinesiophobia-11 (TSK-11) were assessed. Seven months postoperatively, a standardized interview was conducted to identify “return to sport” (RS) and “non-return to sport” (nRS) patients. Logistic regression and “Receiver Operating Characteristic” (ROC) analyses were used to determine predictive parameters. Results No significant differences could be detected between RS and nRS patients concerning socio-demographic data, muscle tests, square hop and TSK-11. In nRS patients, the Limb Symmetry Index (LSI) of single hop for U. Müller (*)  Department of Orthopaedics, Physical Medicine and Rehabilitation, University of Munich, Marchioninistrasse 15, 81377 Munich, Germany e-mail: [email protected]‑muenchen.de M. Krüger‑Franke · B. Rosemeyer  MVZ Nordbad, Schleißheimerstrasse 130, 80797 Munich, Germany M. Schmidt  Department of Medical Informatics, Biometry and Epidemiology of the Faculty of Medicine, University of Munich, Marchioninistrasse 15, 81377 Munich, Germany

distance (p = 0.005), crossover hop (p = 0.008) and triple hop (p = 0.001) were significantly lower, in addition to the ACL–RSI (p  = 0.013) and IKDC 2000 (p  = 0.037). The cut-off points for LSI single hop for distance were 75.4 % (sensitivity 0.74; specificity 0.88), and for ACL–RSI 51.3 points (sensitivity 0.97; specificity 0.63). Logistic regression distinguished between RS and nRS subjects (sensitivity 0.97; specificity 0.63). Conclusions  The single hop for distance and ACL–RSI were found to be the strongest predictive parameters, assessing both the objective functional and the subjective psychological aspects of returning to sport. Both tests may help to identify patients at risk of not returning to pre-injury sport. Level of evidence  II. Keywords  Anterior cruciate ligament rupture · Operative reconstruction · Return to sport · Predictors

Introduction The most common ligament injury of the knee joint is the tearing of the anterior cruciate ligament (ACL) [9, 43]. In Germany, approximately 35,000 ACL ruptures are reported annually (raw incidence 45:100,000), with women being more often affected than men [6, 22]. Most patients harm themselves without direct physical contact, particularly in sports involving pivoting, cutting and jumping [43]. About 28,000 ACL operations are performed in Germany per year [22]. Giving-way episodes, as well as the hope to regain full sport activities, are reasons to consider surgical therapy [2, 6]. With regard to the knee joint, sport activities can be classified into four levels [17]. Level I is comprised of sports that involve jumping, pivoting and hard cutting

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movements, such as football or soccer [17]. Level II describes activities such as tennis or skiing, level III activities such as jogging, cycling or swimming and level IV activities of daily life. If patients want to return to their pre-injury sport level after surgery, the appropriate time point for restarting is essential. Currently, no scientifically established time point exists. Based on empirical data, a number of authors suggest returning to level I and level II sports approximately 6 months post-surgery [2, 13, 15, 29]. According to a review by Barber-Westin et al. [5], one-third of the 264 analysed studies considered the time factor as the only criterion, while only 13 % utilized individual-based objective criteria. This is in line with a recently published review by Petersen and Zantop [39]. Objective criteria, for instance, include muscle strength and single-leg hop tests [5, 13, 16, 24, 33, 47]. Single-leg hop tests allow for a more comprehensive assessment of the functional capacity of the knee joint [29]. The single hop for distance, crossover hop for distance, triple hop for distance and 6-m timed hop test are most often applied [5, 13, 16, 24, 33, 47]. Assessed is the Limb Symmetry Index (LSI), the ratio of the operated leg to the non-operated leg. As a criterion for returning to sport, LSI values of muscle strength and/or single-leg hop tests above 85 % [5, 13, 24, 33] or 90 % [5, 16, 24, 35, 47], respectively, are recommended. For participation in sport activities with frequent pivoting movements, a value of 100 % is suggested [47]. Several authors have proposed decision criteria for returning to sport using special equipment [5, 13, 16, 24, 33, 47]. However, their implementation into daily clinical routine is not possible. Myer et al. [35] took this into account by defining three single-leg hop tests as part of a test battery to evaluate the operated knee. There is strong evidence that psychological factors, such as fear of pain, fear of re-injury and deficient confidence, have a great influence on returning to sport [2, 4, 46]. A considerable number of patients do not return to their pre-injury level of sport despite successful rehabilitation and satisfactory physical recovery [2, 24, 25, 27]. To investigate such psychological factors, various self-report questionnaires are in use, such as the Tampa Scale of Kinesiophobia, the Emotional Response of Athletes to Injury Questionnaire or the Anterior Cruciate Ligament–Return to Sport after Injury Scale [7, 8, 25, 27, 30, 49]. The aim of the study was to define parameters—functional tests and/or self-report questionnaires—that can be used to predict the successful resumption of pre-injury level I and level II sports 6 months after ACL reconstruction. These parameters may be helpful in the clinical decision of clearing a patient to return to sport. The 6-month time point was chosen as many surgeons decide about clearance for returning to sport at this time.

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Knee Surg Sports Traumatol Arthrosc

Materials and methods The study was designed as a prospective controlled trial with a cohort of 40 patients after ACL reconstruction surgery. Patients underwent surgical treatment from July 2011 to March 2012 at Medizinisches Versorgungszentrum (MVZ) Nordbad-Munich. All of the patients received the same treatment and rehabilitation, according to a standard scheme [32]. The surgical treatment consisted of an arthroscopic evaluation of the injured joint and the management of the ruptured ACL in an anatomic single-bundle technique with a fourfold semitendinosus tendon and bioabsorbable interference screw fixation (Matryx, Linvatec–Conmed). Inclusion criteria were an isolated rupture of ACL, age between 18 and 65 years and the intension to return to their pre-injury level I or level II recreational sports [17]. At the 6-month surgeon’s examination, the operated knee joint had to be free of pain, without irritation, and had passively full range of motion. The Lachman and Pivot Shift Test had to be positive. The patients had to be able to stand and hop on the operated leg and did not report a subjective feeling of instability. They had to be able to perform level III activities without symptoms. Permission for returning to pre-injury sport level was given by the surgeon if the above clinical criteria were fulfilled. Exclusion criteria were concomitant injuries, such as injuries involving lateral ligaments or menisci, adjacent joints (hip or foot) or the contralateral leg. Patients with other orthopaedic, internal, neurological or psychiatric diseases, as well as pregnant women, were excluded. From a cohort of 186 operated ACL patients, 112 were excluded due to concomitant or prior injuries or because of age [23]. Fifty-nine of the remaining 74 patients could be contacted for the 6-month examination. Eleven of these patients had not performed any level I and level II sports before surgery. The remaining 48 patients were informed about the study and asked whether they would be willing to participate. At the 6-month examination by the surgeon, 40 of the 48 patients fulfilled the inclusion criteria (Fig. 1). The study was designed according to the guidelines of the Helsinki International Conference on Harmonization—Good Clinical Practice. The ethics committee of the Bavarian State Chamber of Physicians (Landesaerztekammer) stated that no approval for the study was required. All patients in the study signed informed consent prior to inclusion. Assessment instruments and procedure The assessment by the same physical therapist was performed the same day, but subsequent to the surgeon’s examination. The assessment instruments included 4 questionnaires, followed by six functional tests. The first

Knee Surg Sports Traumatol Arthrosc ACL-reconstruction 01.07.2011-31.03.2012 n=186 Isolated ACL rupture n=74

Concomitant injuries, re-rupture, age n=112

No contact n=15 Contacted for study n=59 Level III and IV n=11 Level I and II, Consent to participate n=48

Medical examination n=48 Inclusion criteria not met n=8

Assessment n=40

Telephone interview n=40 Scalet fever n=1 Return to sport n=31

Non return to sport n=8

Fig. 1  Flow chart for participants’ enrolment

questionnaire inquired about socio-demographic data, cause of injury and sports activities (current and before surgery). The second questionnaire was the latest edition [1] of the International Knee Documentation Committee (IKDC) subjective knee evaluation form, a knee-specific 10-item questionnaire measuring symptoms, function and sport activities [20]. The IKDC subjective knee evaluation form is valid and reliable for ACL injuries with a significant test–retest reliability [20] and is used as criterion for returning to sport after ACL reconstruction [13, 33]. The Tampa Scale for Kinesiophobia (TSK) is a questionnaire assessing pain-related fear of movement [21]. It is appropriate for patients after ACL reconstruction [7, 8, 12]. The TSK-11 was shortened from the original version by removing 6 psychometrically weak items, with a total of 11 items remaining on the questionnaire [52]. The validity, reliability and test–retest reliability of both questionnaires are comparable [52]. The Anterior Cruciate Ligament–Return to Sport after Injury Scale (ACL–RSI) is a specific 12-item

questionnaire assessing the psychological impact (emotions, confidence in performance and risk appraisal) of returning to sport after ACL reconstruction surgery [49]. The questionnaire has high reliability, validity and test– retest reliability [26, 49], and was recently translated into German language [31]. For the functional testing, the patient warmed up using stationary cycling at 50 W over 5 min. All functional clinical tests were performed with the non-operated leg first. The tests started with an isometric muscle strength measurement instead of an isokinetic strength measurement [13, 16]. The Pearson correlation coefficient for the relationship between isometric and isokinetic muscle strength measurements in healthy subjects for knee extensors and knee flexors is 0.74 (p