Keywords

1 Introduction

The majority of patients who undergo anterior cruciate ligament (ACL) reconstruction are athletes <25 years of age [1]. While there are several major goals of surgery, returning these individuals to their desired sport is paramount for patient satisfaction [2,3,4,5,6,7,8] and is the main motivating factor for patients to undergo surgery and months of rehabilitation. Physicians and others involved with patient care often believe return to sports (RTS) is one of the most important outcome criteria after ACL reconstruction [9]. The ultimate RTS goals vary widely and include returning professional athletes back to their careers, allowing collegiate athletes to receive scholarships, providing high school athletes a chance to play additional seasons, and returning recreational athletes back to their desired active lifestyle. Although historic rates of RTS have been acceptable, this topic has come under increased scrutiny due to high reinjury rates recently reported (to the ACL in either knee) upon return to athletics after surgery [10].

In addition to reinjury rates, several barriers that prevent or delay full RTS have recently come under rigorous investigation. These include fear, anxiety, depression, preoperative stress, motivation, self-esteem, locus of control, and self-efficacy [3, 7, 11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26]. Persistent knee symptoms of pain, swelling, stiffness, and instability may also hamper the expected progress of rehabilitation and negatively affect the time to RTS [18, 27,28,29].

Even though many studies have reported significant correlations of return to high-risk sports with ACL reinjuries, few have documented the results of rehabilitation in terms of restoration of normal muscle strength, balance, proprioception, and other neuromuscular indices required for return to high-risk activities that require pivoting, cutting, and jumping/landing. In addition, several studies have shown that changes in neurocognitive function and cortical activity occur after ACL injury and reconstruction [30,31,32,33,34,35,36,37]. The question of whether modern rehabilitation programs effectively resolve these impairments remains to be answered [38, 39]. Therefore, reinjuries may not be due simply to participation in high-risk activities; failure to restore multiple indices to normal (in both knees) may be one major source of this problem, and this will be explored later in this textbook.

The question of what factors play a role in the development of knee osteoarthritis (OA) after ACL reconstruction remains under study, with the exception of meniscectomy. Nearly every long-term study has reported a statistically significant correlation between meniscectomy (performed either concurrently or after the ACL reconstruction) and moderate-to-severe radiographic evidence of OA [40,41,42,43,44,45,46,47,48]. Other factors that may influence the development of knee joint OA include preexisting chondral damage, severe bone bruising, biochemical alterations after the injury, older patient age, elevated body mass index (BMI), excessive uncorrected varus or valgus lower limb malalignment, damage of other knee ligaments, failure of the reconstruction to restore knee stability, serious complications (such as infection, arthrofibrosis), and poor quadriceps strength [47, 49,50,51,52,53,54]. Whether return to high-impact sports after ACL reconstruction increases the rate of development of knee OA is unknown at present. Regardless of the cause, the development of symptomatic OA is especially concerning in young athletic individuals, in whom rates of total knee arthroplasty (TKA) continue to rise rapidly. In 2013, Weinstein et al. [55] estimated that over 1.5 million individuals aged 50–69 years had undergone TKA in the USA, tripling the number compared with the proceeding decade. With TKA survival rates of 20 years, many younger individuals may require a revision arthroplasty.

2 Quality of Life and Patient Satisfaction: Correlation with Return to Sport

One major goal of ACL reconstruction is to return patients to their desired sports activity level. Interestingly, a review published in 2015 found that, in 119 ACL-reconstruction studies, only 24% provided return to preinjury sports activity data [56]. The authors recommended enhanced reporting of these data due to the high level of relevance of RTS for both patients and clinicians. In the same year, a survey of 1779 orthopedic medical professionals reported a consensus of six measures believed important for successful outcome 2 years after ACL reconstruction [9]. These measures included no giving-way (indicated by 96.4% of respondents), RTS as indicated by playing 2 seasons at the preinjury level (92.4%), quadriceps strength symmetry >90% (90.3%), absence of joint effusion (84.1%), patient-reported outcomes (83.2%), and hamstrings strength symmetry >90% (83.1%).

Ardern et al. [2] questioned whether satisfaction of knee function according to the patient was associated with different measures, including psychological factors and personal opinion of knee function. These authors followed 177 ACL-reconstructed patients a mean of 3 years postoperatively, of whom 44% were satisfied with their outcome, 28% mostly satisfied, and 28% dissatisfied. There was a significantly greater percentage of patients in the satisfied group that returned to their preinjury sports level compared with the other groups (61%, 29%, and 22%, respectively, P < 0.0001). Participants who had returned to their preinjury activity level had 3 times increased odds of being satisfied (versus mostly satisfied or dissatisfied). The other two significant associations with satisfaction were knee-related self-efficacy and quality of life (QOL).

Another study performed a cross-sectional comparison of patients who underwent either operative or conservative treatment for acute ACL ruptures [57]. At 1 year post-injury or postoperative, 350 ACL-deficient knees and 350 ACL-reconstructed knees completed the Knee Injury and Osteoarthritis Outcome Score (KOOS). The ACL-reconstructed group had higher scores for pain, activities of daily living, sports, and quality of life 1 year postoperatively (Table 1.1). The authors concluded that patients who elected ACL reconstruction had superior outcomes for knee symptoms, function, and quality of life that remained for at least 5 years postoperatively.

Table 1.1 KOOS scores in ACL-deficient and ACL-reconstructed knees at 1 year
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Filbay et al. [4] studied QOL and psychological health outcomes in 162 patients who had residual knee pain, symptoms, or functional limitations a mean of 9 years (range, 5–20) postoperative. These investigators found that RTS was related to better knee-related KOOS and general health-related QOL (AQoL-8D) scores. In this study, 39% returned to competitive sports, 28% returned at a lower level of competition, and 32% did not return. When asked what activities they would consider most important to participate in (in the absence of knee pain), 80% of the patients indicated sports or exercise; 14%, family duties; 4%, social activities; and 2%, work duties. This high rate of patients that preferred sports/exercise over all other activities indicates the high priority athletics had in this cohort many years following their ACL injury and surgery.

Nwachukwu et al. [7] surveyed 231 patients a mean of 3.7 years following ACL reconstruction and reported that 87% had RTS and 85.4% were very satisfied with the outcome of the operation. A significantly greater number of patients who RTS were very satisfied with their outcome compared with those who did not return (P < 0.001). It is important to note that only 43.6% of the athletes played with unlimited effort and performance and no pain. The use of a patellar tendon autograft was associated with a significantly increased odds of returning to play compared with use of an allograft (odds ratio [OR] = 5.6; P = 0.02).

Faltstrom et al. [17] conducted a short-term study (mean follow-up, 1.5 years) in 182 female soccer players who underwent ACL STG autograft reconstruction. The survey study found that 52% were currently playing soccer, 80% at the same or higher preinjury level and 20% at a lower level. Players that returned had significantly higher scores compared with those who had not returned on all KOOS subscales and the ACL-Quality of Life scale. In addition, psychological readiness and motivation to return to sport correlated with return to preinjury levels. The negative effects of fear of reinjury and poor motivation on RTS are further discussed in Chap. 2.

Kocher et al. [5] followed a cohort of 201 patients whose mean age was 28.6 years (range, 14.4–60) an average of 3 years after primary ACL reconstruction. Patients were found to be significantly less satisfied with the outcome of surgery if they had a lower level of sports activity (P < 0.001) and if they had difficulty with specific athletic functions such as running, jumping, cutting, and twisting (P < 0.001). In this study, 75 patients (37%) were participating in sports with no limitations.

3 Reinjury Rates After ACL Reconstruction

The published rates of either reinjuring an ACL-reconstructed knee or sustaining an ACL rupture on the contralateral knee vary widely (Table 1.2) [58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83]. One problem is the definition of ACL failure; some studies consider only those knees that required ACL revision reconstruction (or reconstruction of the contralateral ACL) as failures, while others include knees in which a pivot shift grade 2–3 and/or Lachman grade 2–3 is detected clinically. Large registry studies or those that involved meta-analyzed data typically only used the number of ACL revision cases to calculate failure rates [65, 69, 76, 79, 81, 84]. There are many potential causes of ACL graft failure other than reinjuries that have been discussed in detail elsewhere [85,86,87,88,89,90]. The reinjury and failure rate data in Table 1.2 should therefore be interpreted cautiously.

Table 1.2 Rates of reinjury in ACL-reconstructed and contralateral knees
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Many studies have cited that the most frequent factors that appear to cause graft failure or injury to the contralateral ACL are younger patient age, return to cutting/pivoting sports, and use of an allograft. In a meta-analysis of data from 19 studies, Wiggins et al. [62] reported, in athletes <25 years of age who returned to high-risk sports, a pooled secondary ACL injury rate (to either knee) of 23%. In a group of 1415 patients who underwent ACL autograft reconstruction, Shelbourne et al. [60] reported the risk of subsequent injury to either knee was 17% for patients <18 years of age compared with 7% for patients 18–25 years and 4% for patients >25 years. These authors attributed the reinjuries to the high-risk sports patients had returned to, with basketball and soccer accounting for 67% of the reinjuries. Andernord et al. [84] reported data on 16,930 patients from the Swedish National Knee Ligament Register and found in both males and females a significantly increased twofold risk of revision surgery with ages 13–19 years (P < 0.001). In a separate study, Andernord et al. [91] reported a significantly increased twofold to threefold risk of contralateral ACL reconstruction in patients less than 20 years of age (P < 0.001).

Dekker et al. [83] followed 85 patients who were <18 years of age at the time of ACL autograft reconstruction a mean of 4 years postoperatively. A majority (91%) returned to sports activities; however, 32% suffered a subsequent ACL tear (19% ipsilateral graft tear, 13% contralateral ACL tear, and 1% both knees) a mean of 2.2 years postoperatively. The only significant risk factor associated with reinjury was earlier return to sport (P < 0.05). Longer times before returning to athletics were protective against a second ACL injury (hazard ratio per month, 0.87 for each 1-month increase).

Faltstrom et al. [92] followed 117 female soccer players (mean age, 19.9 ± 2.5 years) a mean of 2 years after primary ACL reconstruction and compared reinjury rates, proportion of players who stopped playing soccer, and patient satisfaction with a matched group of uninjured players. The ACL-reconstructed group had nearly a fivefold higher rate of new ACL injuries (29 versus 8, rate ratio 4.82, P < 0.001), a higher rate of players who stopped playing soccer (62% versus 36%, P = 0.001), and a lower satisfaction rate (47% versus 87%).

Several investigations have reported discouraging percentages of athletes who RTS even though muscle strength and neuromuscular function appeared to be restored to normal levels [28, 29, 93,94,95,96]. A meta-analysis of 69 articles involving 7556 athletes reported that only 65% returned to their preinjury sports level and 55% returned to competitive sports [94]. Factors associated with RTS included symmetrical hopping performance, younger age, male gender, playing elite sports, and having a positive attitude. A study of 205 soccer players reported that only 54% returned to the sport a mean of 3.2 years postoperatively [29]. Of those that returned, 39% experienced pain, 43% had stiffness, and 42% reported instability during or after physical activity. Male gender, no cartilage injury, and no pain during physical activity were associated with greater odds of RTS. An investigation of 99 athletes reported that although 92% returned to sports, only 51% returned to their preinjury level [23]. Factors associated with RTS in this study included female gender and higher scores on the International Knee Documentation Committee (IKDC) Subjective Knee scale and the Lysholm scale. Rosso et al. [28] reported that, although 90% of 161 patients RTS after primary ACL reconstruction, only 58% did so at the preinjury level. The main reasons for not returning were knee symptoms (37%), personal reasons (30%), or both (29%).

A meta-analysis that assessed RTS and reinjury rates of 1008 children and adolescents (aged 6–19) from 19 studies reported a pooled return to preinjury activity level in 79% (range, 41–100%) [97]. ACL reinjury rates were provided for 717 patients, 13% of whom sustained ACL graft ruptures. Contralateral ACL rupture rates were provided for 652 knees, 14% of whom sustained injuries. Ten of the studies reported that the majority of injuries occurred during sports activities.

Critical Points

  • Long-term failure rates vary widely (2–32%).

  • Factors correlated with ACL graft failure: younger age, high sports activity level, vertical graft angle, and use of a small STG autograft or allograft.

  • Contralateral ACL at risk for rupture, higher than ACL graft in some studies.

4 Factors Involved in the Development of Knee Osteoarthritis After ACL Surgery

Long-term clinical studies documenting radiographic OA after ACL reconstruction show high variability in the percent of knees that develop moderate or severe joint damage (Table 1.3) [40, 41, 45,46,47,48, 75, 99,100,101, 103,104,105,106, 108, 110,111,112,113,114]. These studies most frequently used weight-bearing anteroposterior (AP) and posteroanterior radiographs (Fig. 1.1), as well as lateral and Merchant, to determine the presence and severity of OA, although a few used MRI [110, 111, 114, 116, 117] or computed tomography [118]. The two most commonly used radiographic rating systems to classify OA are the Kellgren-Lawrence (K-L) [119] and the IKDC system [120]. It is also important to note that few investigators have determined if OA is accompanied by pain, swelling, and impaired knee function. The longest clinical studies published to date have followed patients for 16–24.5 years postoperatively [102, 121,122,123]. As investigations obtain longer follow-up periods, one may speculate that the OA findings will become more severe and correlate with clinical symptoms such as loss of extension and swelling with daily activities.

Table 1.3 Prevalence of radiographic osteoarthritis in long-term ACL reconstruction studies
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Fig. 1.1
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Standing radiographs of a patient 14 years after a right ACL reconstruction and subsequent medial meniscectomy. The pivot-shift test was negative, indicating a stable reconstruction. However, narrowing to the medial tibiofemoral compartment is evident and the patient demonstrated 2° of varus alignment (Reprinted from Noyes and Barber-Westin [115])

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Studies have shown that, regardless of the outcome of ACL reconstruction in terms of restoration of knee stability, meniscectomy accelerates degenerative joint changes [40, 41, 45,46,47,48, 124, 125]. Claes et al. [43] systematically reviewed 16 long-term ACL reconstruction studies (follow-up range, 10–24.5 years) involving 1554 subjects. The investigators reported that the estimate for the prevalence of moderate to severe OA (IKDC ratings of C or D) for all patients was 27.9%. The prevalence of OA was 16.4% in patients with isolated ACL injuries and 50.4% in patients with concurrent meniscectomy (OR 3.54).

Barenius et al. [41] followed 164 patients a mean of 14 years after ACL reconstruction and reported symptomatic OA (K-L grade ≥2) in 57% of ACL-reconstructed knees compared with 18% of contralateral knees. Statistically significant risk factors for medial tibiofemoral OA were BMI ≥25 kg/m2 at follow-up (OR 3.3), manual labor (OR 3.2), positive pivot shift at 2-year follow-up (OR 2.5), and medial meniscectomy (OR 4.2). Statistically significant risk factors for lateral tibiofemoral OA were lateral meniscectomy (OR 5.1) and use of a B-PT-B autograft (OR 2.3). Statistically significant risk factors for patellofemoral OA were BMI ≥25 kg/m2 at follow-up (OR 3.5) and medial meniscectomy (OR 2.3). There was no significant difference in the prevalence of OA between the two graft types.

We conducted a systematic review of the treatment of meniscus tears during ACL reconstruction of studies published from 2001 to 2011 [126]. Data on 11,711 meniscus tears (in 19,531 patients) from 159 studies showed that 65% were treated by meniscectomy; 26%, by repair; and 9%, by no treatment. This was concerning because many meniscus tears can be successfully treated by repair, thereby salvaging this important structure.

It is important to note that there are many factors other than meniscectomy that may influence the development of knee joint OA, including preexisting chondral damage, severe bone bruising, biochemical alterations in the knee joint after the injury, older patient age, elevated BMI, failure of the reconstruction to restore normal AP displacement, complications (such as infection, arthrofibrosis), and poor quadriceps strength [47, 49,50,51,52,53,54]. In many studies, these variables are not controlled for, making reaching conclusions on these factors difficult.

Occult injuries to the bone, commonly referred to as bone bruises , occur with ACL ruptures in 80–100% of knees (Fig. 1.2) [127,128,129,130,131,132,133]. Occult osteochondral lesions vary, and therefore, the relationship between the presence of these injuries with ACL ruptures and subsequent OA remains unclear. Several studies have reported that bone bruises resolve with time [110, 132, 134]. Conversely, Frobell [134] followed 61 consecutive patients who had acute ACL injuries with MRI within 4 weeks of the injury and then 2 years later. Subjects were treated either with early ACL reconstruction (34 subjects), delayed ACL reconstruction (11 subjects), or rehabilitation alone (16 subjects). Posttraumatic bone marrow lesions noted in the lateral tibiofemoral compartment resolved in 57 of 61 knees by 2 years after the ACL injury. However, new lesions developed in the lateral tibiofemoral joint for unknown reasons in one-third of the population, and significant thinning of the cartilage in the trochlea was noted that was not detected during the baseline MRI. Evidence does exist that the most severe injuries are associated with future cartilage degeneration, and they therefore should be considered part of the sequela of post-traumatic OA.

Fig. 1.2
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Bone bruise on MRI following rupture of the ACL

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A few studies that longitudinally followed patients with acute ACL ruptures for several years demonstrated a strong potential for joint deterioration [54, 131, 134]. For instance Potter et al. prospectively followed 40 patients who underwent baseline MRI within 8 weeks of the injury and again 7–11 years later [131]. The MRI evaluation used a cartilage-sensitive, pulse sequence evaluation with T2 techniques which have shown increased ability to detect traumatic chondral injuries. None of the patients had concurrent damage to the menisci or other knee ligaments or an articular cartilage lesion rated as Outerbridge grade 3 or higher. ACL reconstruction was performed in 28 patients, while no surgery was done in 14. At baseline, all knees had an MRI-detectable cartilage injury, most severely over the lateral tibial plateau. Regardless of surgical intervention, by 7–11 years after injury, the risk of cartilage damage as viewed on MRI for the lateral femoral condyle was 50 times that of baseline, 30 times for the patella, and 18 times for the medial femoral condyle. The nonsurgical group had a significantly higher OR effect of cartilage loss over the medial tibial plateau compared with the surgical group.

ACL ruptures create biochemical alterations in the knee joint which many investigators hypothesize play a major role in the development of OA [135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150]. The sequence of events begins immediately after the injury and continues for years thereafter (Table 1.4) [135, 136, 149]. The injury causes collagen rupture, joint hemarthrosis, subchondral bone edema, elevated glycosaminoglycan (GAG) levels, and cell necrosis. In the ensuing months, the inflammatory process (indicated by elevated levels of several cytokine mediators such as IL-1β, IL-6, and tumor necrosis factor α [TNFα]), decrease in lubricin concentrations, release of enzymes, production of metalloproteinase (MMP), degradation of the extracellular matrix and proteoglycans, chondrocyte apoptosis, and cell death all contribute to articular cartilage deterioration.

Table 1.4 Pathogenesis of posttraumatic articular cartilage deterioration after ACL injury
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Our analysis of current long-term studies provided no answer regarding the potential deleterious effect of returning to high athletic activity levels on subsequent risk of symptomatic OA. One may hypothesize that knees with intact menisci and no other ligament damage (that do not sustain reinjuries) will have no statistically significant increased risk for symptomatic OA compared with matched controls. The need to preserve meniscal function remains paramount for the long-term welfare of the joint, and we have long advocated meniscal repair for tears in the red/red (periphery) and red/white (central) regions (Fig. 1.3) [152,153,154,155,156]. Complex tears are evaluated on an individual basis for repair potential (Fig. 1.4). The indications and contraindications for meniscus repair procedures have been discussed in detail elsewhere [153]. Our long-term study (10–22 years) of single longitudinal meniscus repairs that extended into the central region in patients ≤20 years of age showed the potential longevity of this procedure [155]. Twenty-nine repairs were evaluated; 18 by follow-up arthroscopy, 19 by clinical evaluation, 17 by MRI, and 22 by weight-bearing posteroanterior radiographs. A 3 T MRI scanner with cartilage-sensitive pulse sequences was used and T2 mapping was performed (Fig. 1.5). We found that 18 (62%) of the meniscus repairs had normal or nearly normal characteristics. Six repairs (21%) required arthroscopic resection, two had loss of joint space on radiographs, and three that were asymptomatic failed according to MRI criteria. There was no significant difference in the mean T2 scores in the menisci that had not failed between the involved and contralateral tibiofemoral compartments. There were no significant differences between the initial and long-term evaluations for pain, swelling, jumping, patient knee condition rating, or the Cincinnati rating score. The majority of patients were participating in sports without problems, which did not affect the failure rate. The outcomes support the recommendation in younger active patients to spend as much time and attention to a meniscus repair as a concurrent ACL reconstruction, as the eventual function of the knee joint is equally dependent on the success of the both structures

Fig. 1.3
figure 3

Meniscus repair instead of meniscectomy to preserve knee joint function. A longitudinal meniscal tear site demonstrates some fragmentation inferiorly. This tear required multiple superior and inferior vertical divergent sutures to achieve anatomic reduction (Reprinted from Noyes and Barber-Westin [152])

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Fig. 1.4
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Arthroscopic visualization of a lateral meniscus root tear. (a) A double locking loop stitch (NovoStitch, Ceterix) is placed through the meniscus at the tear site (b). Three loop stitches were used to achieve a high strength fixation (c). Final configuration of the lateral meniscus repair with the meniscus pulled flush to the repair site (d) (Reprinted from Noyes and Barber-Westin [115])

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Fig. 1.5
figure 5

T2 MRI of a 37-year-old male 17 years post-ACL reconstruction and lateral meniscus repair. The patient was asymptomatic with light sports activities. The lateral meniscus repair healed and the ACL reconstruction restored normal stability. Prolongation of T2 values is noted over the posterior margin with adjacent subchondral sclerosis (arrow) (Reprinted from Noyes et al. [155])

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Critical Points

  • Majority OA mild or moderate; presence of associated symptoms not reported in most studies.

  • Meniscectomy correlates with radiographic evidence of osteoarthritis (OA) in nearly all long-term studies in which cohorts are sorted according to intact versus meniscectomized knees.

  • Other risk factors associated with OA after ACL reconstruction include preexisting chondral damage, severe bone bruising, biochemical alterations, patient age, body mass index, failure of the reconstruction to restore normal anteroposterior displacement, complications, and poor quadriceps strength.

  • ACL injury causes collagen rupture, joint hemarthrosis, subchondral bone edema, elevated glycosaminoglycan levels, and cell necrosis.

  • Bone bruises 80–100% acute ACL rupture, natural history unclear.

  • Large severe bone bruises associated with subchondral or osteochondral injuries may persist for years after injury.

  • Consider most severe bone injuries part of sequela of post-traumatic OA.

  • We have long advocated repair of meniscus tears when appropriate indications met to preserve this vital structure.