Functional recovery after anterior cruciate ligament reconstruction: a longitudinal perspective

Joint contributions to sagittal plane total support moment in patients with knee osteoarthritis after anterior cruciate ligament reconstruction

BACKGROUND

Patients with anterior cruciate ligament reconstruction (ACLR) demonstrate lower knee loading. This study aimed to determine whether sagittal plane TSM and joint contributions to total support moment (TSM) in the surgical limb are different between athletes who did and did not show radiological features of knee OA at 2 years after ACLR during triple hops (TH), single hop (TH), single-legged vertical jump (VJ), and walking.

METHODS

Forty-one athletes with 2 years of unilateral ACLR surgery participated in this cross-sectional study. Athletes completed motion analysis testing of single-legged TH, SH, VJ, and walking tasks. Sagittal plane TSM and individual joint (ankle, knee, and hip) contributions to TSM were computed at peak knee flexion angle (TSM-PKF). Posterior-anterior radiographs were completed in standing and 30° knee flexion. Kellgren-Lawrence (KL) system was used to identify radiological features of knee OA in the medial compartment of the reconstructed knee (OA-group: KL ≥2; Non-OA group: KL<2).

RESULTS

There was a significant group-by-joint-by-task interaction for joint contributions to TSM-PKF (p = 0.012), with the OA-group (n = 13) had lower knee and higher hip contributions compared to the non-OA group during TH, SH, and VJ (p ≤ 0.049). There was a significant joint-by-group interaction for the joint contributions to TSM-PKF (p = 0.004), with the OA-group having lower knee (p = 0.003) and higher hip (p = 0.001) contributions compared to the Non-OA group.

SIGNIFICANCE

The OA-group exhibited lower knee and higher hip contributions to the sagittal plane TSM compared to the Non-OA group during the landing phase of single-limb high-demand activities. The OA-group exhibited decreased knee loading and compensated by shifting the mechanical load to the hip joint within the reconstructed knee. Decreased knee loading in the OA-group may have affected the required mechanical loading to maintain knee metabolism and integrity.

A New Way to Restrict Free Leg Movement During Unilateral Vertical Jump Test

The purpose of this investigation was (1) to test the effect of movement restriction of the free leg during unilateral vertical jump on performance and power output comparing 2 different jump techniques: flexed (Classic technique) and straight (FC Luzern technique) free leg, and (2) to test the correlation between performance and power output obtained using these 2 techniques. Twenty elite soccer players performed squat (SJ) and countermovement (CMJ) jumps on each leg. The jump height and peak power output were compared between the 2 techniques for both legs. The jump height and peak power were significantly higher for the classic test for SJ and CMJ (P < .001) with no side effects or interactions. The angular range of motion of the free leg was higher for the Classic test than for the FC Lucerne test (P < .001), with no difference in the angular range of motion of the trunk. A moderate correlation was found between the 2 techniques on peak power (SJ: r = .626; CMJ: r = .649) and jump height (SJ: r = .742; CMJ: r = .891). Consequently, FC Lucerne technique, limiting the contribution of the free leg, is more appropriate to assess lower limb strength capacities during unilateral jump test.

Effects of a Perioperative Blood Flow Restriction Therapy Program on Early Quadriceps Strength and Patient-Reported Outcomes After Anterior Cruciate Ligament Reconstruction

Background

Quadriceps muscle atrophy remains a limiting factor in returning to activity after anterior cruciate ligament reconstruction (ACLR). Blood flow restriction (BFR) therapy may accelerate quadriceps strengthening in the perioperative period.

Purpose

To evaluate postoperative isometric quadriceps strength in patients who underwent ACLR with a perioperative BFR program.

Study Design

Randomized controlled trial; Level of evidence, 1.

Methods

Patients indicated for ACLR were randomized into 2 groups, BFR and control, at their initial clinic visit. All patients underwent 2 weeks of prehabilitation preoperatively, with the BFR group performing exercises with a pneumatic cuff set to 80% limb occlusion pressure placed over the proximal thigh. All patients also underwent a standardized postoperative 12-week physical therapy protocol, with the BFR group using pneumatic cuffs during exercise. Quadriceps strength was measured as peak and mean torque during seated leg extension and presented as quadriceps index (percentage vs healthy limb). Patient-reported outcomes (PROs), knee range of motion, and quadriceps circumference were also gathered at 6 weeks, 3 months, and 6 months postoperatively, and adverse effects were recorded.

Results

Included were 46 patients, 22 in the BFR group (mean age, 25.4 ± 10.6 years) and 24 in the control group (mean age, 27.5 ± 12.0 years). At 6 weeks postoperatively, the BFR group demonstrated significantly greater strength compared with the controls (quadriceps index: 57% ± 24% vs 40% ± 18%; P = .029), and the BFR group had significantly better Patient-Reported Outcomes Measurement Information System-Physical Function (42.69 ± 5.64 vs 39.20 ± 5.51; P = .001) and International Knee Documentation Committee (58.22 ± 7.64 vs 47.05 ± 13.50; P = .011) scores. At 6 weeks postoperatively, controls demonstrated a significant drop in the peak torque generation of the operative versus nonoperative leg. There were no significant differences in strength or PROs at 3 or 6 months postoperatively. Three patients elected to drop out of the BFR group secondary to cuff intolerance during exercise; otherwise, no other severe adverse events were reported.

Conclusion

Integrating BFR into perioperative physical therapy protocols led to improved strength and increased PROs at 6 weeks after ACLR. No differences in strength or PROs were found at 3 and 6 months between the 2 groups.

Registration

NCT04374968 (ClinicalTrials.gov identifier).

Residual Deficits in Reactive Strength After Anterior Cruciate Ligament Reconstruction in Soccer Players

CONTEXT

Deficits in plyometric abilities are common after anterior cruciate ligament reconstruction (ACLR). Vertical rebound tasks may provide a targeted evaluation of knee function.

OBJECTIVE

To examine the utility of a vertical hop test for assessing function after ACLR and establishing factors associated with performance.

DESIGN

Cross-sectional study.

SETTING

Rehabilitation program.

PATIENTS OR OTHER PARTICIPANTS

Soccer players with a history of ACLR (n = 73) and matched control individuals (n = 195).

MAIN OUTCOME MEASURE(S)

The 10-second vertical hop test provided measures of jump height, the Reactive Strength Index (RSI), and asymmetry. We also examined possible predictors of hop performance, including single-legged vertical drop jump, isokinetic knee-extension strength, and the International Knee Documentation Committee questionnaire score.

RESULTS

Between-limbs differences were identified only for the ACLR group, and asymmetry scores increased in those with a history of ACLR (P < .001) compared with the control group. The single-legged vertical drop jump, RSI, and knee-extension torque were significant predictors of 10-second hop height (R2 = 20.1%) and RSI (R2 = 47.1%).

CONCLUSIONS

Vertical hop deficits were present after ACLR, even after participants completed a comprehensive rehabilitation program. This may have been due to reduced knee-extension and reactive strength. Vertical hop tests warrant inclusion as part of the return-to-sport test battery.

Is It Time We Better Understood the Tests We are Using for Return to Sport Decision Making Following ACL Reconstruction? A Critical Review of the Hop Tests

There has been a move towards a criterion-based return to play in recent years, with 4 single-leg hop tests commonly used to assess functional performance. Despite their widespread integration, research indicates that relationships between ‘passing’ ‘hop test criteria and successful outcomes following rehabilitation are equivocal, and, therefore, require further investigation. This critical review includes key information to examine the evolution of these tests, their reliability, relationships with other constructs, and sensitivity to change over time. Recommendations for how measurement and administration of the tests can be improved are also discussed. The evidence presented in this review shows that hop tests display good reliability and are sensitive to change over time. However, the use of more than 2 hop tests does not appear to be necessary due to high collinearity and no greater sensitivity to detect abnormality. The inclusion of other hop tests in different planes may give greater information about the current function of the knee, particularly when measured over time using both relative and absolute measures of performance. It is recommended that the contralateral limb be tested prior to surgery for a more relevant benchmark for performance, and clinicians are strongly advised to measure movement quality, as hop distance alone appears to overestimate the recovery of the knee.

Evolution of Functional Recovery using Hop Test Assessment after ACL Reconstruction

The purpose of this study was to evaluate improvements in functional performance through the use of the Limb Symmetry Index of Single and Triple Hop tests between 12 and 52 weeks after anterior cruciate ligament reconstruction, and to compare these values with usual time-based and performance-based criteria used during the return to sport continuum. Repeated functional assessments using Single and Triple Hop Tests at 12, 16, 22, 26, 39 and 52 postoperative weeks were evaluated. At each session, the median and interquartile range of Limb Symmetry Index of tests were calculated and compared with the usual criteria: return to participation:≥85%, between 12-16 w; return to play:≥90%, between 26-39 w. The results indicate that the median increased over time to 39 postoperative weeks and then stabilized. For Single Hop Test, wide variability was seen at 12 and 16 weeks (interquartile range=20%); this was lower from 22 to 52 weeks (interquartile range=8-6%). At 12 weeks for Single Hop Test, the median was 83.6% and did not meet>85% criteria for return to participation. Hop tests could be interesting functional tests to follow the functional recovery and help decision-making regarding return to participation and return to play.

Strength and functional symmetry is associated with post-operative rehabilitation in patients following anterior cruciate ligament reconstruction

PURPOSE

To investigate strength and functional symmetry during common tests in patients after anterior cruciate ligament reconstruction (ACLR), and its association with post-operative rehabilitation.

METHODS

At a median 11.0 months post-surgery (range 10-14), 111 ACLR patients were assessed. A rehabilitation grading tool was employed to evaluate the duration and supervision of rehabilitation, as well as whether structured jumping, landing and agility exercises were undertaken. Patients completed the Noyes Activity Score (NSARS), maximal isokinetic knee extensor and flexor strength assessment, and a 4-hop test battery. Limb Symmetry Indices (LSIs) were calculated, presented for the entire group and also stratified by activity level. ANOVA evaluated differences between the operated and unaffected limbs across all tests. Correlations were undertaken to assess the relationship between post-operative rehabilitation and objective test LSIs.

RESULTS

The unaffected limb was significantly better (p < 0.0001) than the operated limb for all tests. Only 52-61 patients (47-55%) demonstrated LSIs ≥ 90% for each of the hop tests. Only 34 (30.6%) and 61 (55.0%) patients were ≥ 90% LSI for peak quadriceps and hamstring strength, respectively. Specifically in patients actively participating in jumping, pivoting, cutting, twisting and/or turning sports, 21 patients (36.8%) still demonstrated an LSI < 90% for the single hop for distance, with 37 patients (65.0%) at < 90% for peak knee extension strength. Rehabilitation was significantly associated with the LSIs for all tests.

CONCLUSION

Rehabilitation was significantly correlated with limb symmetry, and lower limb symmetry was below recommended criterion for many community-level ACLR patients, including those already engaging in riskier activities. It is clear that many patients are not undertaking the rehabilitation required to address post-operative strength and functional deficits, and are being cleared to return to sport (or are returning on their own accord) without appropriate evaluation and further guidance.

LEVEL OF EVIDENCE

IV.

Single-Shot Femoral Nerve Block Does Not Cause Long-Term Strength and Functional Deficits Following Anterior Cruciate Ligament Reconstruction

PURPOSE

To determine if patients treated with a single-shot femoral nerve block have strength and functional deficits at 9-month follow-up.

METHODS

Forty-three patients who underwent primary anterior cruciate ligament reconstructions were randomized to receive either a preoperative single-shot femoral nerve block or local infiltration anesthesia for primary pain control. All patients underwent a standardized comprehensive rehabilitation program postoperatively. Isokinetic strength and function was tested using a Biodex machine at 9 months or more postoperatively comparing the operative and nonoperative extremity.

RESULTS

No significant difference in strength was found at an average of 10.6 months postoperatively (range, 9-15 months) between the femoral nerve block and control groups. In comparing strength deficits, we found no difference in slow isokinetic extension strength (22.4% vs 27.8%, P = .51), fast isokinetic extension strength (18.5% vs 12.5%, P = .41), slow isokinetic flexion strength (11.0% vs 15.1%, P = .55), and fast isokinetic flexion strength (8.2% vs 4.9%, P = .56) in the femoral nerve block versus control groups, respectively. In terms of functional outcomes, there also was no difference in deficits for single-leg hop distance (P = .12), timed single-leg hop (P = .74), and single-leg triple hop distance (P = .94). Maximal strength noted to be within 15% of the contralateral limb was achieved in 40% of patients and maximal function in 63% of patients at an average of 10.6 months postoperatively. A 13% complication rate was found in patients who received a femoral nerve block (1 with prolonged quadriceps inhibition and 2 with prolonged sensory disturbances).

CONCLUSIONS

Our study found a 13% motor/sensory complication rate in patients who underwent femoral nerve block for pain control after anterior cruciate ligament reconstruction. Although these deficits may persist, they are not permanent and are not different when compared with controls at 9-month follow-up. However, maximal strength and function are not fully restored at normal return to play time and rehabilitation should continue long term to maximize recovery.

LEVEL OF EVIDENCE

Level I, prospective randomized trial.

Relationships of Muscle Function and Subjective Knee Function in Patients After ACL Reconstruction

BACKGROUND

After anterior cruciate ligament reconstruction (ACLR), relationships between objective measures of muscle function and patient-reported outcomes may change over time. Examining these measures at different time frames after surgery may help develop individualized approaches to improve post-ALCR analysis.

PURPOSE

To examine the associations between subjective knee function and lower-extremity muscle function in individual patients at various time points after ACLR.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Fifty-one participants who underwent primary, unilateral ACLR (15 males, 36 females; mean age, 22.9 ± 4.5 years; mean height, 172.4 ± 10.1 cm; mean weight, 68.7 ± 13.1 kg) were separated into 3 groups depending on time since surgery (early, <2 years; middle, 2-5 years; late, >5 years). Subjective knee function was quantified using the International Knee Documentation Committee (IKDC) subjective knee form and the Knee injury and Osteoarthritis Outcome Score (KOOS). Isometric knee extension and flexion strength were collected at 90 deg/s. Single-leg hop performance was measured using the single hop, triple hop, cross-over hop, and 6-m timed hop. Coefficient correlations were calculated between subjective knee function and objective measures of muscle function for each group.

RESULTS

The early group demonstrated moderate correlations between the KOOS and unilateral measures of flexion peak torque (r = 0.514, P = .035) and flexion power (r = 0.54, P = .027). The middle group demonstrated the strongest correlations between the KOOS and symmetry measures of the single hop (r = 0.69, P = .002) and extension work (r = 0.71, P = .002) as well as unilateral measures of the triple hop (r = 0.52, P = .034) and extension work (r = 0.66, P = .004). The late group demonstrated strong correlations between the 6-m timed hop symmetry and the IKDC (r = 0.716, P = .001) and KOOS (r = 0.71, P = .001).

CONCLUSION

Patients with a post-ACLR status of less than 2 years exhibited stronger relationships with unilateral strength measures to subjective function; graft type was found to change these relationships. Patients at 2 to 5 years postsurgery demonstrated relationships with both unilateral and symmetry measures of muscle function to subjective function. Patients who were more than 5 years after ACLR exhibited strong associations between hopping symmetry and subjective function.

CLINICAL RELEVANCE

Future clinical guidelines for patients after ACLR may need to consider time since surgery as a potential factor.

Impaired voluntary quadriceps force control following anterior cruciate ligament reconstruction: relationship with knee function

PURPOSE

Impairments in quadriceps force control and altered quadriceps and hamstring muscle activation strategies have been observed following anterior cruciate ligament reconstruction; however, the functional implications of these impairments are unclear. This study examined the cross-sectional associations between quadriceps force control, quadriceps activation, hamstring coactivation and clinically assessed knee function following anterior cruciate ligament reconstruction with a hamstring graft.

METHODS

Sixty-six patients (18 ± 3 months following surgery) and 41 uninjured individuals participated. Quadriceps force control was assessed using an isometric knee extension task. Participants cyclically increased and decreased quadriceps force at slow speeds between 5 and 30 % maximum voluntary isometric contraction matching a moving target displayed on a screen. Quadriceps activation and hamstring coactivation were assessed concurrently using surface electromyography. Knee function was assessed with the Cincinnati Knee Rating Scale and three single-leg hop tests.

RESULTS

The reconstructed group completed the task with 48 % greater root-mean-square error (RMSE), indicating significantly worse quadriceps force control (p < 0.001). In a multivariable model adjusted for sex, greater RMSE and greater lateral hamstring coactivation were significantly associated with worse knee function that is greater odds of scoring <85 % on one or more knee functional assessment.

CONCLUSIONS

Less-accurate quadriceps force output and greater hamstring coactivation are associated with worse knee joint function following anterior cruciate ligament reconstruction and may contribute to irregular knee joint loading and the onset or progression of knee osteoarthritis. Impairments in quadriceps force control and altered muscle activation strategies may be modifiable through neuromuscular training, and this is an area for future research.

LEVEL OF EVIDENCE

Case-control study, Level III.

Do Patients Failing Return-to-Activity Criteria at 6 Months After Anterior Cruciate Ligament Reconstruction Continue Demonstrating Deficits at 2 Years?

BACKGROUND

The variability in outcomes after anterior cruciate ligament reconstruction (ACLR) might be related to the criteria that are used to determine athletes' readiness to return to their preinjury activity level. A battery of return-to-activity criteria (RTAC) that emphasize normal knee function and movement symmetry has been instituted to quantitatively determine athletes' readiness to return to preinjury activities.

PURPOSE

To investigate performance-based and patient-reported measures at 12 and 24 months after ACLR between patients who passed or failed RTAC at 6 months after ACLR.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 108 patients who had participated in International Knee Documentation Committee level 1 or 2 sports activities completed RTAC testing at 6, 12, and 24 months after surgery. The RTAC included the isometric quadriceps strength index (QI), 4 single-legged hop tests, the Knee Outcome Survey-activities of daily living subscale (KOS-ADLS), and the global rating scale of perceived function (GRS). Patients who scored ≥90% on all RTAC were classified as the pass group, and those who scored <90% on any RTAC were classified as the fail group. At 12- and 24-month follow-ups, patients were asked if they had returned to the same preinjury activity level.

RESULTS

At the 6-month follow-up, there were 48 patients in the pass group and 47 in the fail group. At the 12-month follow-up, 31 patients (73.8%) from the pass group and 15 patients (39.5%) from the fail group passed RTAC, and at the 24-month follow-up, 25 patients (75.8%) from the pass group and 14 patients (51.9%) from the fail group passed RTAC. The rate of return to activities in the pass group was 81% and 84% at 12 and 24 months after ACLR, respectively, compared with only 44% and 46% in the fail group ( P ≤ .012), respectively; however, some patients in the fail group participated in preinjury activities without being cleared by their therapists. At 12 and 24 months, 60.5% and 48.1% of patients continued to fail again on the criteria, respectively. A statistically significant group × time interaction was found for the single hop and 6-m timed hop limb symmetry indices (LSIs) ( P ≤ .037), with only the fail group demonstrating a significant improvement over time. A main effect of group was detected for the QI and the crossover hop and triple hop LSIs ( P < .01), with patients in the pass group demonstrating higher performance. A main effect of time was detected for the crossover hop and triple hop LSIs and the GRS, with improvements seen in both groups ( P < .05).

CONCLUSION

Patients who passed the RTAC early after ACLR were more likely to demonstrate normal knee function and movement symmetry at 12 and 24 months postoperatively, while patients who failed the RTAC early were more likely to demonstrate impaired knee function and movement asymmetry at 12- and 24-month follow-ups. Patients in the pass group had a higher rate of return to their preinjury activity level compared with those in the fail group. A group of patients chose to return to their preinjury activities, even though they were functionally not ready.

Evaluation of static and dynamic balance in athletes with anterior cruciate ligament injury - A controlled study

OBJECTIVES

Anterior cruciate ligament injury leads to adaptive responses to maintain postural control. However, there is no consensus regarding whether leg dominance also affects postural control in athletes with anterior cruciate ligament injury. The purpose of this study was to evaluate dynamic and static postural control among athletes with and without anterior cruciate ligament injury to the dominant leg.

METHODS

Twenty-eight athletes, twenty-one males and seven females aged 15-45 years, were allocated to one of two groups: the anterior cruciate ligament injury group (26±3 years) or the control group without anterior cruciate ligament injury (25±6.5 years). All subjects performed one legged stance tests under eyes open and eyes closed conditions and squat and kick movement tests using a postural control protocol (AccuSwayPlus force platform, Massachusetts). The center of pressure displacement and speed were measured by the force platform. In addition, the distance traveled on the single-leg hop test was assessed as an objective measure of function.

RESULTS

Significantly greater mediolateral sway was found under the eyes closed condition (p=0.04) and during squat movement (p=0.01) in the anterior cruciate ligament injury group than in the control group. Analysis of the single-leg hop test results showed no difference between the groups (p=0.73).

CONCLUSION

Athletes with anterior cruciate ligament injury had greater mediolateral displacement of the center of pressure toward the dominant leg under the eyes closed condition and during squat movement compared to control athletes.

A conceptual framework for a sports knee injury performance profile (SKIPP) and return to activity criteria (RTAC)

Injuries to the knee, including intra-articular fractures, ligamentous ruptures, and meniscal and articular cartilage lesions, are commonplace within sports. Despite advancements in surgical techniques and enhanced rehabilitation, athletes returning to cutting, pivoting, and jumping sports after a knee injury are at greater risk of sustaining a second injury. The clinical utility of objective criteria presents a decision-making challenge to ensure athletes are fully rehabilitated and safe to return to sport. A system centered on specific indicators that can be used to develop a comprehensive profile to monitor rehabilitation progression and to establish return to activity criteria is recommended to clear athletes to begin a progressive and systematic approach to activities and sports. Integration of a sports knee injury performance profile with return to activity criteria can guide clinicians in facilitating an athlete's safe return to sport, prevention of subsequent injury, and life-long knee joint health.

Are practice trials required for hop tests?

Single-legged hop tests are commonly used in clinic and research settings to obtain information on functional performance of the injured leg. When performing these tests, it is typical to provide a few practice trials before performing actual test trials. However, the importance of practice trials and how it affects performance during actual test trials are not known. This study investigated the effect of practice trials on single-leg hop performance using a marker-based kinematic tracking approach in individuals with anterior cruciate ligament (ACL) reconstruction and athletic controls. Thirteen subjects with ACL reconstruction and thirteen uninjured healthy subjects performed the single hop for distance test for both legs. Three practice and five test trials were performed on each leg. Single-leg hop distance scores and hop indices (i.e., side-to-side hop distance ratios) obtained from practice and test trials were compared. There were significant differences in the mean hop distance between practice and test trials (P<0.05) when raw scores were compared, but no differences were observed when comparing the side-to-side distance ratios (P>0.05). There were also significantly high correlations between practice and test trials (P<0.01) and the agreement between practice and test scores was very good (ρc=0.88-0.98). The findings suggest that subjects indeed improve their performance during test trials; however, the improvements had an inconsequential effect on the side-to-side hop distance ratios. Therefore, if the examiner is interested only in side-to-side ratios, then practice trials can be minimized or even avoided to improve efficiency and minimize time and costs associated with additional trials.

Return to play following anterior cruciate ligament reconstruction

In athletes, significant advances in anterior cruciate ligament reconstruction techniques and rehabilitation have led to improved surgical outcomes and increased expectations for return to play. Although an expeditious return to sport has become an achievable and often realistic goal, the factors that most influence safe, timely, and successful return to play remain unknown. The literature offers mainly anecdotal evidence to guide the team physician in the decision-making process, with a paucity of criteria and consensus guidelines available to help determine return to sport. Attempts have been made to introduce criteria-based progression in the rehabilitation process, but validation of subjective and objective criteria has been difficult. Nevertheless, several pertinent factors in the preoperative, intraoperative, and postoperative periods may affect return to play following anterior cruciate ligament reconstruction. Further research is warranted to validate reliable, consensus guidelines with objective criteria to facilitate the return to play process.

Controversies in knee rehabilitation: anterior cruciate ligament injury

Controversy in management of athletes exists after anterior cruciate ligament (ACL) injury and reconstruction. Consensus criteria for evaluating successful outcomes following ACL injury include no reinjury or recurrent giving way, no joint effusion, quadriceps strength symmetry, restored activity level and function, and returning to preinjury sports. Using these criteria, the success rates of current management strategies after ACL injury are reviewed and recommendations are provided for the counseling of athletes after ACL injury.

Deconstructing the Anterior Cruciate Ligament: What We Know and Do Not Know About Function, Material Properties, and Injury Mechanics

Anterior cruciate ligament (ACL) injury is a common and potentially catastrophic knee joint injury, afflicting a large number of males and particularly females annually. Apart from the obvious acute injury events, it also presents with significant long-term morbidities, in which osteoarthritis (OA) is a frequent and debilitative outcome. With these facts in mind, a vast amount of research has been undertaken over the past five decades geared toward characterizing the structural and mechanical behaviors of the native ACL tissue under various external load applications. While these efforts have afforded important insights, both in terms of understanding treating and rehabilitating ACL injuries; injury rates, their well-established sex-based disparity, and long-term sequelae have endured. In reviewing the expanse of literature conducted to date in this area, this paper identifies important knowledge gaps that contribute directly to this long-standing clinical dilemma. In particular, the following limitations remain. First, minimal data exist that accurately describe native ACL mechanics under the extreme loading rates synonymous with actual injury. Second, current ACL mechanical data are typically derived from isolated and oversimplified strain estimates that fail to adequately capture the true 3D mechanical response of this anatomically complex structure. Third, graft tissues commonly chosen to reconstruct the ruptured ACL are mechanically suboptimal, being overdesigned for stiffness compared to the native tissue. The net result is an increased risk of rerupture and a modified and potentially hazardous habitual joint contact profile. These major limitations appear to warrant explicit research attention moving forward in order to successfully maintain/restore optimal knee joint function and long-term life quality in a large number of otherwise healthy individuals.

Functional Performance Testing After Anterior Cruciate Ligament Reconstruction: A Systematic Review

Background:

When to allow an athlete to return to unrestricted sporting activity after anterior cruciate ligament (ACL) reconstruction remains controversial.

Purpose:

To report the results of functional performance testing reported in the literature for individuals at differing time points following ACL reconstruction and to examine differences between graft types.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A systematic review of Medline, Scopus, and Cochrane Central Register of Controlled Trials was performed using PRISMA guidelines. Inclusion criteria were English-language studies that examined any functional rehabilitation test from 6 months to 2 years following ACL reconstruction. All patient-, limb-, and knee-specific demographics were extracted from included investigations. All functional rehabilitation tests were analyzed and compared when applicable.

Results:

The search term returned a total of 890 potential studies, with 88 meeting inclusion and exclusion criteria. A total of 4927 patients were included, of which 66% were male. The mean patient age was 26.5 ± 3.4 years. The predominant graft choices for reconstruction were bone–patellar tendon–bone (BPTB) autograft (59.8%) and hamstring autograft (37.9%). The most commonly reported functional tests were the hop tests. The results of these functional tests, as reported in the Limb Symmetry Index (LSI), improved with increasing time, with nearly all results greater than 90% at 1 year following primary ACL reconstruction. At 6 months postoperatively, a number of isokinetic strength measurements failed to reach 80% LSI, most commonly isokinetic knee extension testing in both BPTB and hamstring autograft groups. The knee flexion strength deficit was significantly less in the BPTB autograft group as compared with those having hamstring autograft at 1 year postoperatively, while no significant differences were found in isokinetic extension strength between the 2 groups.

Conclusion:

Hop testing was the most commonly reported functional test following ACL reconstruction. Increases in performance on functional tests were predictably seen as time increased following surgery. Those with hamstring autografts may experience increased strength deficits with knee flexion versus those having BPTB autograft. These data provide information that may assist providers in determining timing of return to unrestricted sporting activity.

Symmetry restoration and functional recovery before and after anterior cruciate ligament reconstruction

PURPOSE

The aims of this study were to evaluate the functional recovery before and after ACL reconstruction and to evaluate the sensitivity to change in performance-based and self-reported outcomes prior to and after ACL reconstruction and to determine whether these changes represent clinically relevant improvement.

METHODS

Eighty-three athletes participated in this study. Athletes were tested after an ACL injury, after preoperative training, and 6 and 12 months after ACL reconstruction. Athletes completed quadriceps strength testing, hop testing, and self-reported questionnaires for knee function (International Knee Documentation Committee subjective knee form, Knee Outcome Survey-Activities of Daily Living Scale, and the Global Rating Scale of Perceived Function) at each testing period.

RESULTS

A significant interaction of limb by time was seen in normalized quadriceps strength, and single, triple, and 6-m timed hop, where the involved limb improved more than the uninvolved limb over time. A main effect of time was noted for performance-based limb symmetry indexes and self-reported measures.

CONCLUSION

Limb-to-limb asymmetries are reduced, and normal limb symmetry is restored after perturbation training and aggressive quadriceps strengthening and returned to similar levels 6 months after reconstruction. Performance-based values on the involved limb and self-reported outcomes are sensitive to change over time, and these were clinically relevant improvements.

Single-legged hop tests as predictors of self-reported knee function after anterior cruciate ligament reconstruction: the Delaware-Oslo ACL cohort study

BACKGROUND

Single-legged hop tests are commonly used functional performance measures that can capture limb asymmetries in patients after anterior cruciate ligament (ACL) reconstruction. Hop tests hold potential as predictive factors of self-reported knee function in individuals after ACL reconstruction.

HYPOTHESIS

Single-legged hop tests conducted preoperatively would not and 6 months after ACL reconstruction would predict self-reported knee function (International Knee Documentation Committee [IKDC] 2000) 1 year after ACL reconstruction.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

One hundred twenty patients who were treated with ACL reconstruction performed 4 single-legged hop tests preoperatively and 6 months after ACL reconstruction. Self-reported knee function within normal ranges was defined as IKDC 2000 scores greater than or equal to the age- and sex-specific normative 15th percentile score 1 year after surgery. Logistic regression analyses were performed to identify predictors of self-reported knee function within normal ranges. The area under the curve (AUC) from receiver operating characteristic curves was used as a measure of discriminative accuracy.

RESULTS

Eighty-five patients completed single-legged hop tests 6 months after surgery and the 1-year follow-up with 68 patients classified as having self-reported knee function within normal ranges 1 year after reconstruction. The crossover hop and 6-m timed hop limb symmetry index (LSI) 6 months after ACL reconstruction were the strongest individual predictors of self-reported knee function (odds ratio, 1.09 and 1.10) and the only 2 tests in which the confidence intervals of the discriminatory accuracy (AUC) were above 0.5 (AUC = 0.68). Patients with knee function below normal ranges were over 5 times more likely of having a 6-m timed hop LSI lower than the 88% cutoff than those with knee function within normal ranges. Patients with knee function within normal ranges were 4 times more likely to have a crossover hop LSI greater than the 95% cutoff than those with knee function below normal ranges. No preoperative single-legged hop test predicted self-reported knee function within normal ranges 1 year after ACL reconstruction (all P > .353).

CONCLUSION

Single-legged hop tests conducted 6 months after ACL reconstruction can predict the likelihood of successful and unsuccessful outcome 1 year after ACL reconstruction. Patients demonstrating less than the 88% cutoff score on the 6-m timed hop test at 6 months may benefit from targeted training to improve limb symmetry in an attempt to normalize function. Patients with minimal side-to-side differences on the crossover hop test at 6 months possibly will have good knee function at 1 year if they continue with their current training regimen. Preoperative single-legged hop tests are not able to predict postoperative outcomes.

The impact of quadriceps femoris strength asymmetry on functional performance at return to sport following anterior cruciate ligament reconstruction

STUDY DESIGN

Cross-sectional study.

OBJECTIVES

To investigate the impact of quadriceps femoris (QF) muscle strength asymmetry at the time of return to sport on self-reported function and functional performance of individuals following anterior cruciate ligament reconstruction (ACLR).

BACKGROUND

Evidence-based QF strength guidelines for return-to-sport decision making are lacking. Objective guidelines necessitate understanding the impact of QF strength deficits at the time of return to sport on function and performance.

METHODS

Fifty-five individuals (mean age, 17.3 years) who were cleared for return to sport following primary ACLR (ACLR group) and 35 uninjured individuals (mean age, 17.0 years) in a control group participated in the study. QF strength (maximum voluntary isometric contraction) was assessed, and the quadriceps index (QI) was calculated [(involved strength/uninvolved strength) × 100%]. The ACLR group was further subdivided into 2 groups, based on the QI: high quadriceps (QI of 90% or greater) and low quadriceps (QI of less than 85%). The International Knee Documentation Committee Subjective Knee Evaluation Form score was used to assess self-reported function, and hop tests were used to assess functional performance. Multivariate analysis of variance and hierarchical regression analyses were performed.

RESULTS

The individuals in the ACLR group were weaker, reported worse function, and performed worse on hop tests compared to those in the control group (P<.05). The low-quadriceps group demonstrated worse performance on the hop tests compared to the high-quadriceps group and the control group (P ≤.016). Hop test performance did not differ between the high-quadriceps and control groups (P ≥.14). QF strength predicted performance on the hop tests beyond graft type, presence of meniscus injury, knee pain, and knee symptoms.

CONCLUSION

At the time of return to sport, individuals post-ACLR who had weaker QF (QI of less than 85%) demonstrated decreased function, whereas those with minimal QF strength deficits (QI of 90% or greater) demonstrated functional performance similar to uninjured individuals. QF strength deficits predicted hop test performance beyond the influences of graft type, presence of meniscus injury, knee pain, and knee symptoms.

The current evidence for treatment of ACL injuries in children is low: a systematic review

BACKGROUND

There is no consensus on the management of anterior cruciate ligament (ACL) injuries in skeletally immature children, and the methodological quality of published studies is questionable. The transphyseal reconstructions, physeal-sparing reconstructions, and nonoperative treatment algorithms that are advocated have little support in the literature. The purpose of this study was to systematically review the methodological quality of the literature on the management of ACL injuries in skeletally immature children.

METHODS

We performed a literature search with use of PubMed to identify prospective or retrospective studies whose primary aim was to assess the outcome after operative or nonoperative treatment of ACL injuries in skeletally immature children. To be included in the analysis, a study had to have a mean duration of follow-up of at least two years and a minimum of ten children in the study had to be verified to be skeletally immature. The methodological quality of the included studies was evaluated with use of the Coleman Methodology Score.

RESULTS

No randomized controlled trials, two prospective cohort studies, and twenty-nine retrospective studies met the inclusion criteria. The Coleman Methodology Score averaged 44.7 ± 9.2 out of 100 (range, 28 to 62). The methodological deficiencies were most evident with regard to the number of included children, the study design, and the description of rehabilitation protocols, outcome criteria, and outcome assessments.

CONCLUSIONS

Caution is necessary when interpreting the results of studies on the treatment of ACL injuries in skeletally immature children because of widespread methodological deficiencies. There is a need for appropriately sized prospective studies and detailed descriptions of rehabilitation programs.

Longitudinal changes in the lower extremity functional scale after anterior cruciate ligament reconstructive surgery

OBJECTIVE

To describe the pattern of change in lower extremity physical function status as measured by the Lower Extremity Functional Scale (LEFS) during the first 16 weeks after anterior cruciate ligament (ACL) reconstructive surgery and illustrate how this information can be applied in clinical practice to assist with goal setting and the evaluation of patient outcomes. The secondary objective is to estimate the test-retest reliability of the LEFS in this population.

DESIGN

Prospective cohort, observational.

SETTING

Physiotherapy private practice.

PATIENTS

Forty-seven participants underwent ACL reconstructive surgery and were initially recruited. Two participants were excluded from the analysis, resulting in 45 participants (28 men, mean age 29.4 years; 17 women, mean age 29.0 years).

INTERVENTIONS

Participants underwent a rehabilitation protocol.

MAIN OUTCOME MEASURES

Participants completed the LEFS at each visit from their initial physiotherapy session to 16 weeks postsurgery. A nonlinear model of change was developed, which related LEFS scores to weeks postsurgery. Test-retest reliability was examined between the seventh and ninth weeks using intraclass correlation coefficients (ICC2,1) and standard error of measurement (SEM).

RESULTS

The nonlinear model demonstrated rapid improvements in LEFS scores within the first 7 to 8 weeks with a gradual tapering of this improvement. At 16 weeks, the predicted LEFS score was 63 out of a maximum score of 80. The LEFS demonstrated excellent test-retest reliability in this population (ICC2,1 = 0.90, SEM = 3.7).

CONCLUSIONS

This study provides a description of postsurgical change in functional status for patients after ACL reconstructive surgery that can assist clinicians in developing clinical goals.

CLINICAL RELEVANCE

A rapid improvement in lower extremity physical function is demonstrated in the first 7 to 8 weeks after ACL reconstructive surgery with a tapering of this improvement after 8 weeks.

Correlation of single leg vertical jump, single leg hop for distance, and single leg hop for time

OBJECTIVES

To determine the correlation among three functional tests: single leg vertical jump (SLVJ), single leg hop for distance (SLHD), and single leg hop for time (SLHT).

DESIGN

Prospective correlational investigation.

SETTING

University research laboratory.

PARTICIPANTS

Forty healthy men (n = 19) and women (n = 21) between the ages of 18 and 30 (23.9 ± 2.0 years).

MAIN OUTCOME MEASURES

SLVJ was measured using the Vertec. SLHD was measured using a standard tape measure. SLHT was measured over a 10-m course using a standard stopwatch.

RESULTS

The strongest correlation was between SLHT and SLHD, -0.89 and -0.89 for dominant and non-dominant lower extremities (LE), respectively. The weakest pairwise correlation was between SLVJ and SLHT, -0.71 and -0.63 for dominant and non-dominant LE, respectively. The correlation between SLVJ and SLHD was 0.74 and 0.71 for dominant and non-dominant LE, respectively.

CONCLUSION

There is a strong correlation between SLHT and SLHD, suggesting that each test measures similar constructs of function, while the modest correlation between SLVJ and SLHT suggest these two tests do not measure the same functional components, and could be paired as outcome measures for the clinical assessment of lower extremity function.

Asymmetrical lower extremity loading after ACL reconstruction: more than meets the eye

Sports fans know that movement patterns are important for athletic performance. Similarly, clinicians know that addressing abnormal movement patterns after an anterior cruciate ligament (ACL) reconstruction is important for a successful return to sport. The kinematic (motion) component of movement patterns is more easily observed than the kinetic (forces) component, thus more commonly addressed in ACL reconstruction rehabilitation. Ignoring the kinetic component, though, could impede a successful return to sport. Asymmetrical lower extremity loading has been reported in a variety of activities following ACL reconstruction, and may contribute to both short- and long-term consequences. It is important that clinicians become aware of the potential for asymmetrical lower extremity loading to affect patient outcomes and for researchers to enlarge the body of knowledge.

Return-to-play in sport: a decision-based model

OBJECTIVE

Return-to-play (RTP) decisions are fundamental to the practice of sports medicine but vary greatly for the same medical condition and circumstance. Although there are published articles that identify individual components that go into these decisions, there exists neither quantitative criteria nor a model for the sequence or weighting of these components within the medical decision-making process. Our objective was to develop a decision-based model for clinical use by sports medicine practitioners.

DATA SOURCES

English literature related to RTP decision making.

MAIN RESULTS

We developed a 3-step decision-based RTP model for an injury or illness that is specific to the individual practitioner making the RTP decision: health status, participation risk, and decision modification. In Step 1, the Health Status of the athlete is assessed through the evaluation of Medical Factors related to how much healing has occurred. In Step 2, the clinician evaluates the Participation Risk associated with participation, which is informed by not only the current health status but also by the Sport Risk Modifiers (eg, ability to protect the injury with padding, athlete position). Different individuals are expected to have different thresholds for "acceptable level of risk," and these thresholds will change based on context. In Step 3, Decision Modifiers are considered and the decision to RTP or not is made.

CONCLUSIONS

Our model helps clarify the processes that clinicians use consciously and subconsciously when making RTP decisions. Providing such a structure should decrease controversy, assist physicians, and identify important gaps in practice areas where research evidence is lacking.

Autologous chondrocyte implantation versus microfracture for knee cartilage injury: a prospective randomized trial, with 2-year follow-up

The objective was to evaluate the functional performance over a 2-year period following autologous chondrocyte implantation (ACI) in an open knee procedure compared to microfracture. Objective functional outcome was studied as secondary analysis in a subgroup of patients, in a randomized clinical trial, with concealed allocation and independent evaluators. Sixty-seven patients with local cartilage defect, with a mean size of 2.4 cm(2) (SD 1.5) of the femoral condyle of the knee were included. Thirty-three patients underwent the microfracture and 34 the ACI procedure. An identical rehabilitation protocol was implemented for both groups. Active knee flexion and extension range, anterior laxity, knee extension strength (concentric at 60 degrees/s) and single leg hop performance (single hop, crossover triple hop and 6 m timed hop test) were evaluated pre-surgery and at 6, 9,12 and 24 months post-surgery. We calculated the symmetry index for individual and four performance tests pooled. Mixed linear model analyses were used with confidence interval set at 95%. The change over 2 years for the pooled performance-based tests was comparable between the two treatment arms. At 2 years, 70% (38/54) of all patients returned to >85% symmetry in overall functional performance. A decrease in functional performance at 6 months following ACI resulted in slower recovery at 9 and 12 months compared to microfracture. Rehabilitation following both cartilage repair procedures is a lengthy process. At 2 years after surgery, ACI patients have similar overall functional outcome compared to microfracture patients.