Effect of Age and Body Mass Index on Time to Advanced Imaging and Surgery in Young Athletes With Anterior Cruciate Ligament Injury

Background

In young athletes with anterior cruciate ligament (ACL) injury, increased times from injury to magnetic resonance imaging (MRI) and injury to surgery can lead to the accrual of new injuries over time.

Purpose

To determine the patient characteristics associated with differences in timing between injury, MRI, and surgery in young athletes with ACL tears.

Study Design

Case-control study; Level of evidence, 3.

Methods

We reviewed the electronic medical records of patients aged 13 to 25 years who underwent isolated primary ACL reconstruction between January 2017 and June 2020 at a single orthopaedic surgery department. The times from injury to MRI, MRI to surgery, and injury to surgery were documented. Patient demographic data (age, sex, body mass index [BMI], race and ethnicity, and insurance type) were recorded. Multivariable analysis was used to determine if any patient characteristic had a significant association with increased time to MRI or surgery.

Results

A total of 369 patients (mean age, 18.0 years; 56% female) were included. Both age and BMI were found to be significantly associated with timing of care while holding all other predictors constant. For every 1-year increase in patient age, time from injury to MRI increased by 9.6 days (95% CI, 1.8-17.4 days; P = .02), time from MRI to surgery increased by 7.4 days (95% CI, 4.4-10.5 days; P < .001), and time from injury to surgery increased by 17.0 days (95% CI, 8.4-25.6 days; P < .001). Compared with patients with normal BMI, overweight patients (BMI range, 25-29.9 kg/m2) had an MRI-to-surgery time that was on average 37.2 days (95% CI, 11.7-62.7 days; P < .004) longer and an injury to surgery time that was on average 71.8 days (95% CI, 0.5-143.0 days; P = .048) longer. Obese patients (BMI ≥30 kg/m2) did not demonstrate a significant relationship with the studied time intervals.

Conclusion

Increasing age and elevated BMI were found to be associated with increased time to MRI and surgical care in young athletes with ACL injuries.

Comparison of physical therapy utilization, timing of return-to-sport test completion, and hop test performance by age and between sexes in youth athletes after anterior cruciate ligament reconstruction

OBJECTIVE

To compare physical therapy (PT) utilization, timing of return-to-sport (RTS) test and hop test performance by age and between sexes in youth after anterior cruciate ligament reconstruction (ACLR).

DESIGN

Multicenter retrospective cohort.

METHODS

A retrospective review of adolescents after primary ACLR was conducted. Participants completed return-to-sport (RTS) tests including single-legged hop testing. PT frequency, average weekly visits, and timing of RTS test were calculated. T-tests assessed the effect of age and sex on average weekly PT visits and multivariable logistic regressions assessed odds of passing hop tests.

RESULTS

289 participants were included (15.7 ± 1.9 years). There was no difference in average weekly PT visits (p = 0.321) or time to RTS test (p = 0.162) by age. There were significant differences in average weekly PT visits (p = 0.047) and mean time from surgery to RTS test (p = 0.048) between sexes with small effect sizes (d = 0.24 and d = 0.21, respectively). Age and sex had no effect on odds of passing hop tests (OR, 1.29; 95% CI, 0.71-2.35 and OR, 0.79; 95%CI, 0.43-1.45, respectively).

CONCLUSION

In a youth cohort, age and sex may have no clinically important effect on PT visit utilization, timing of RTS test or hop test performance.

Relationship Between Age and Pathology With Treatment of Pediatric and Adolescent Discoid Lateral Meniscus: A Report From the SCORE Multicenter Database

BACKGROUND

Surgical treatment options of discoid lateral meniscus in pediatric patients consist of saucerization with or without meniscal repair, meniscocapular stabilization, and, less often, subtotal meniscectomy.

PURPOSE

To describe a large, prospectively collected multicenter cohort of discoid menisci undergoing surgical intervention, and further investigate corresponding treatment of discoid menisci.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A multicenter quality improvement registry (16 institutions, 26 surgeons), Sports Cohort Outcomes Registry, was queried. Patient characteristics, discoid type, presence and type of intrasubstance meniscal tear, peripheral rim instability, repair technique, and partial meniscectomy/debridement beyond saucerization were reviewed. Discoid meniscus characteristics were compared between age groups (<14 and >14 years old), based on receiver operating characteristic curve, and discoid morphology (complete and incomplete).

RESULTS

In total, 274 patients were identified (mean age, 12.4 years; range, 3-18 years), of whom 55.6% had complete discoid. Meniscal repairs were performed in 55.1% of patients. Overall, 48.5% of patients had rim instability and 36.8% had >1 location of peripheral rim instability. Of the patients, 21.5% underwent meniscal debridement beyond saucerization, with 8.4% undergoing a subtotal meniscectomy. Patients <14 years of age were more likely to have a complete discoid meniscus (P < .001), peripheral rim instability (P = .005), and longitudinal tears (P = .015) and require a meniscal repair (P < .001). Patients ≥14 years of age were more likely to have a radial/oblique tear (P = .015) and require additional debridement beyond the physiologic rim (P = .003). Overall, 70% of patients <14 years of age were found to have a complete discoid meniscus necessitating saucerization, and >50% in this young age group required peripheral stabilization/repair.

CONCLUSION

To preserve physiological "normal" meniscus, a repair may be indicated in >50% of patients <14 years of age but occurred in <50% of those >14 years. Additional resection beyond the physiological rim may be needed in 15% of younger patients and 30% of those aged >14 years.

Age, Sex, and BMI Differences Related to Repairable Meniscal Tears in Pediatric and Adolescent Patients

BACKGROUND

The incidence of meniscus tears and ACL tears in pediatric patients continues to rise, bringing to question the risk factors associated with these injuries. As meniscus tears are commonly repaired in pediatric populations, the epidemiology of repairable meniscus tears is an important for consideration for surgeons evaluating treatment options.

PURPOSE

To describe meniscal tear patterns in pediatric and adolescent patients who underwent meniscal repair across multiple institutions and surgeons, as well as to evaluate the relationship between age, sex, and body mass index (BMI) and their effect on the prevalence, type, and displacement of repaired pediatric meniscal tears.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Data within a prospective multicenter cohort registry for quality improvement, Sport Cohort Outcome Registry (SCORE), were reviewed to describe repaired meniscal tear patterns. All consecutive arthroscopic meniscal repairs from participating surgeons in patients aged <19 years were analyzed. Tear pattern, location, and displacement were evaluated by patient age, sex, and BMI. A subanalysis was also performed to investigate whether meniscal tear patterns differed between those occurring in isolation or those occurring with a concomitant anterior cruciate ligament (ACL) injury. Analysis of variance was used to generate a multivariate analysis of specified variables. Sex, age, and BMI results were compared across the cohort.

RESULTS

There were 1185 total meniscal repairs evaluated in as many patients, which included 656 (55.4%) male and 529 (44.6%) female patients. Patients underwent surgery at a mean age of 15.3 years (range, 5-19 years), with a mean BMI of 24.9 (range, 12.3-46.42). Of the 1185 patients, 816 (68.9%) had ACL + meniscal repair and 369 (31.1%) had isolated meniscal repair. The male patients underwent more lateral tear repairs than the female patients (54.3% to 40.9%; P < .001) and had a lower incidence of medial tear repair (32.1% vs 41.4%; P < .001). Patients with repaired lateral tears had a mean age of 15.0 years, compared with a mean age of 15.4 years for patients with repaired medial or bilateral tears (P = .001). Higher BMI was associated with "complex" and "radial" tear repairs of the lateral meniscus (P < .001) but was variable with regard to medial tear repairs.

CONCLUSION

In pediatric and adolescent populations, the data suggest that the surgical team treating knees with potential meniscal injury should be prepared to encounter more complex meniscal tears, commonly indicated in those with higher BMI, while higher rates of lateral meniscal tears were seen in male and younger patients. Future studies should analyze correlates for meniscal repair survival and outcomes in this pediatric cohort undergoing knee surgery.

A Corresponding Point Measurement System Provides Reliable Measurement of Displacement for Medial Epicondyle Fractures

Little consensus exists on the best method for evaluation and management of pediatric medial epicondyle fractures because of an inability to reliably evaluate fracture displacement with standard imaging techniques. This study aimed to determine the performance of various radiographic views in evaluating displaced medial epicondyle fractures when using a standardized measurement methodology.

METHODS

Ten fellowship-trained pediatric orthopaedic surgeons assessed fracture displacement in 6 patients with displaced medial epicondyle fractures using radiographic views (anteroposterior, lateral, axial, internal oblique [IO], and external oblique [EO]) and computed tomographic (CT) views (axial, 3-dimensional [3D] horizontal, and 3D vertical). Raters used a corresponding point method for measuring displacement. For each image, raters measured the absolute displacement, categorized the percent of displacement relative to the size of the fragment and fracture bed, and indicated a treatment option. Interobserver reliability was calculated for each view. Bland-Altman plots were constructed to evaluate the bias between each radiograph and the mean of the CT methods.

RESULTS

For absolute displacement, anteroposterior and EO views showed almost perfect interobserver reliability, with an interclass correlation coefficient (ICC) of 0.944 for the anteroposterior view and an ICC of 0.975 for the EO view. The axial view showed substantial reliability (ICC = 0.775). For the displacement category, almost perfect reliability was shown for the anteroposterior view (ICC = 0.821), the axial view (ICC = 0.911), the EO view (ICC = 0.869), and the IO view (ICC = 0.871). Displacement measurements from the anteroposterior, axial, and EO views corresponded to the measurements from the CT views with a mean bias of <1 mm for each view. However, the upper and lower limits of agreement were >5 mm for all views, indicating a substantial discrepancy between radiographic and CT assessments. Treatment recommendations based on CT changed relative to the recommendation made using the anteroposterior view 29% of the time, the EO view 41% of the time, and the axial view 47% of the time.

CONCLUSIONS

Using a corresponding point measurement system, surgeons can reliably measure and categorize fracture displacement using anteroposterior, EO, and axial radiographic views. CT-based measurements are also reliable. However, although the mean difference between the radiograph-based measurements and the CT-based measurements was only about 1 mm, the discrepancy between radiographic views and CT-based methods could be as large as 5 to 6 mm.

LEVEL OF EVIDENCE

Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Adolescent Baseball Pitchers With Ulnar Collateral Ligament Tears Exhibit a High Proportion of Partial Tears

BACKGROUND

Ulnar collateral ligament (UCL) tears in the throwing elbow are classified according to grade and location using magnetic resonance arthrography (MRA). However, the frequency of each tear type and the association to age, competition level, and radiographic findings in adolescent baseball pitchers are unknown.

PURPOSES

The primary purpose of this study was to use MRA to characterize the severity, location, and UCL tear type in adolescent pitchers. The second aim was to describe the relationship between the UCL tear type and age, competition level, and plain radiographic findings.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Records of adolescent pitchers with a UCL tear treated by the senior author between 2007 and 2016 were retrospectively reviewed. MRA scans were reviewed and tears were classified according to the Joyner-Andrews classification. Low-grade partial tears are classified as type I, high-grade partial tears as type II, complete full-thickness tears as type III, and tear pathology in >1 region in the UCL as type IV. Each type of tear also has a location designated at the midsubstance, ulna (U), or humerus (H). Patient characteristics, competition level, and associated plain radiographic abnormalities were recorded. Univariate analyses were performed to examine the relationships between tear types and age, competition level, and plain radiographic findings.

RESULTS

A total of 200 adolescent pitchers (mean ± SD age, 17.2 ± 1.5 years) with MRA scans were reviewed. Type II-H (n = 62), type II-U (n = 51), and type III-U (n = 28) were the most common tear types observed. Type II tears comprised 64.5% of adolescent UCL tears, with type II-H being the most common. Plain radiographs were abnormal in 32% of patients, with calcifications (10.5%) and olecranon osteophytes (12.5%) being the most common findings. There were no significant relationships between tear type and age (P = .25), competition level (P = .23), or radiographic abnormalities (P = .75).

CONCLUSION

Humeral-sided high-grade partial tears were the most common tear type in adolescent pitchers. There was no relationship between UCL tear type and age competition level, and plain radiographic abnormalities.

Adolescent Patients Exhibit Significant Improvements in Strength and Functional Performance From 6 to 9 Months After ACL Reconstruction With Quadriceps Autograft

Purpose

To investigate differences between the 6-month and 9-month return to sport (RTS) assessments in adolescent patients undergoing anterior cruciate ligament reconstruction (ACLR) with quadriceps tendon autograft.

Methods

A retrospective review was performed of consecutive adolescent patients who underwent ACLR between June 2017 and October 2019. Patients completed a structured RTS test 6 and 9 months after surgery consisting of isometric and isokinetic strength testing, the Lower Quarter Y-Balance Test, and single-legged hop testing. The recovery of muscle strength, assessed via isometric/isokinetic and hop testing, was defined by a limb symmetry index (LSI) ≥90%. Differences were compared between the 2 RTS test time points.

Results

In total, 27 patients (16 female, 11 male) were identified with a mean age of 15 years (range, 13-17 years). There were statistically significant improvements in isometric quadriceps strength (LSI, 85.0 ± 17.2 vs 92.5 ± 11.3; P = .04) and hamstring strength (LSI, 87.9 ± 11.2 vs 99.0 ± 10.5; P < .01). There were improvements in isokinetic knee extension at both 60°/s (LSI, 75.2 ± 16.7 vs 83.3 ± 13.8) and 180°/s (LSI, 79.9 ± 15.4 vs 83.4 ± 11.2), but the differences were only statistically significant at 60°/s (P = .02 and P = .17, respectively). There were no significant differences in isokinetic testing of knee flexion at either 60°/s or 180°/s. There were no statistically significant differences in the anterior reach component of the Lower Quarter Y-Balance Test at 6 and 9 months. Patients demonstrated statistically significant improvements on single- legged hop testing with mean LSIs >95% for each of the 4 tests at 9 months postop.

Conclusions

Adolescent patients undergoing ACLR with quadriceps tendon autograft demonstrated significant improvements in quadriceps strength between 6 and 9 months postoperatively.

Level of Evidence

Level IV, therapeutic case series.

Outcomes and Return to Sport After Ulnar Collateral Ligament Reconstruction in Adolescent Baseball Players

Background:

The number of ulnar collateral ligament (UCL) reconstructions in adolescent athletes has increased over the past 2 decades. Clinical results in this population have not been well studied.

Purpose/Hypothesis:

The purpose of this study was to evaluate the outcomes and return to sport after UCL reconstruction in a large group of adolescent baseball players. We hypothesized that excellent clinical outcomes and high rates of return to sport would be observed in this population at a minimum 2-year follow-up.

Study Design:

Case series; Level of evidence, 4.

Methods:

We reviewed 140 adolescent (aged ≤19 years) baseball players who underwent UCL reconstruction with the American Sports Medicine Institute (ASMI) technique by a single surgeon. Medical records were reviewed for patient demographics, injury characteristics, operative details, and surgical complications. Patient-reported outcomes were assessed using the Conway scale, the Andrews-Timmerman (A-T) score, the Kerlan-Jobe Orthopaedic Clinic (KJOC) score, and a 0- to 100-point subjective scale for elbow function and satisfaction. Return to sporting activity was assessed using a custom-designed questionnaire.

Results:

The mean age at the time of surgery was 18.0 years (range, 13-19 years), and the mean follow-up was 57.9 months (range, 32.4-115.4 months). Over half (60%) of patients were high school athletes. The mean duration of symptoms before surgery was 6.9 months (range, 0.5-60.0 months). Partial tears were identified in 57.9% of patients, and 41.3% of patients had preoperative ulnar nerve symptoms. Graft type included the ipsilateral palmaris in 77.1% of patients. Concomitant procedures were performed in 25% of patients. Outcomes on the Conway scale were “excellent” in 86.4% of patients. The mean A-T and KJOC scores were 97.3 ± 6.1 and 85.2 ± 14.6, respectively. Mean patient satisfaction was 94.4. Overall, 97.8% of patients reported returning to sport at a mean of 11.6 months (range, 5-24 months), and 89.9% of patients returned to sport at the same level of competition or higher. A total of 11.6% of patients went on to play professional baseball.

Conclusion:

UCL reconstruction with the ASMI technique is an effective surgical option in adolescents, with excellent outcome scores. At a minimum of 2-year follow-up, nearly 90% of patients returned to their preinjury level of sport.

Differences in Segmental Speeds as a Function of Maturation in Youth Baseball Pitchers

The purpose of this study was to determine how stride length, segmental sequencing of the pelvis, trunk, humerus, and forearm velocities and accelerations, and the timing of these values change as youth mature. Thirteen youth baseball pitchers participated at three consecutive time points: visit 1 (10.7±1.3 years; 151.8±10.7 cm; 45.0±9.65 kg), visit 2 (11.5±1.6 years; 155.5±11.1 cm; 50.4±10.0 kg), and visit 3 (12.4±1.7 years; 161.5±11.7 cm; 56.4±10.8 kg). Participants executed three pitches for a strike to a catcher. The maximum value of stride length and segmental speeds and accelerations was recorded. The point at which these maximum values occurred during the throw was calculated as a percentage from hand separation to maximum internal rotation of the shoulder. Repeated measures ANOVAs and Friedman Tests revealed no statistically significant differences between stride length, segmental speeds and accelerations, and their percentage of the pitch between the three visits. However, there was a significant increase in ball velocity across visits. No significant changes occurred in pitching mechanics between the ages of 10–12. The authors speculate the lack of differences can be accounted for because these ages are prior to any significant pubescent changes. Future research should consider pre- and post- pubescent age groups.

Outcomes and Return to Sport After Revision Anterior Cruciate Ligament Reconstruction in Adolescent Athletes

Background

The number of adolescent anterior cruciate ligament (ACL) injuries is rising with increased participation in higher level athletics at earlier ages. With an increasing number of primary ACL reconstructions (ACLRs) comes a rise in the incidence of revision ACLRs.

Purpose

To evaluate the clinical results of revision ACLR across a group of high-level adolescent athletes with at least 2-year follow-up.

Study Design

Case series; Level of evidence, 4.

Methods

A retrospective review of 21 adolescent athletes (age range, 10-19 years) who underwent revision ACLR with at least 2-year follow-up was conducted. Patient-reported outcome measures (PROMs) included the International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form, Lysholm knee scoring scale, Tegner activity level scale, and modified Cincinnati Knee Rating System. Return to sport (RTS) and overall patient satisfaction were also assessed.

Results

The mean age at the time of surgery was 16.5 years (range, 14-19 years), and the mean follow-up was 46.4 months (range, 24-97 months); 42.9% of patients were female, and 52.4% of patients participated in collision sports. The mean time to failure after primary ACLR was 13.1 ± 8.0 months, and the most common mechanism of failure was noncontact in at least 66.7% of cases. The revision graft type included bone-patellar tendon-bone (BPTB) in 71.4% of cases; 26.7% of BPTB grafts were from the contralateral extremity. Concomitant procedures were performed for intra-articular lesions in 71.4% of patients. The mean patient satisfaction rate was 95.3%. There were 3 cases of a graft reinjury at a mean of 25 months postoperatively. The mean PROM scores were as follows: IKDC, 87.5 ± 12.7; Tegner, 7.2 ± 2.0; Lysholm, 93.7 ± 9.8; and Cincinnati, 93.4 ± 10.0. Of those attempting to RTS, 68.4% of patients successfully returned at the same level of competition. Patients with a lateral compartment chondral injury were less likely to RTS (P < .05). Independent variables shown to have no significant relationship to PROMs or RTS included age, follow-up, sport classification, associated meniscal tears, revision graft size/type, and concomitant procedures.

Conclusion

Revision ACLR can be an effective surgical option in adolescents participating in collision and contact sports, with good to excellent subjective outcome scores. At a minimum 2-year follow-up, a graft rupture after revision ACLR occurred in 14% of cases. Of the athletes attempting to RTS, 68.4% returned to their preinjury level of competition.

Lateral Patellofemoral Ligament Reconstruction With a Gracilis Allograft

Isolated medial patellar subluxation (MPS), in the absence of a previous lateral retinacular release, is a poorly recognized clinical condition characterized by chronic anterior knee pain that is exacerbated with knee flexion. This type of patellar instability is often overlooked, and a high index of suspicion is needed for appropriate diagnosis and treatment. The purpose of this Technical Note is to describe a surgical technique to reconstruct the lateral patellofemoral ligament with an allograft gracilis tendon. By restoring stability to the lateral side of the patella, this minimally invasive technique successfully treats cases of isolated MPS.

Clinical results after treatment for bidirectional patellar subluxation: Minimum 2-years follow-up

BACKGROUND

We describe the preliminary clinical results of a patellar stabilization technique to treat bidirectional patellar subluxation (BPS).

METHODS

Patients: six patients (one male, five females; mean age 30.2years) underwent this procedure with a minimum of 24months follow-up. Patients were assessed for clinical instability, patellar complications, and need for revision surgery. Patient functional outcomes were evaluated using the criteria of Crosby and Insall and the Kujala Anterior Knee Pain Scale at the time of final follow-up. Patient satisfaction was assessed using a subjective questionnaire.

OPERATIVE TECHNIQUE

A semitendinosus tendon autograft is coursed through a transverse tunnel in the distal quadriceps tendon. The medial and lateral aspects of the graft are passed from the quadriceps tendon within subfascial tunnels to the MPFL attachment site and lateral epicondyle, respectively. The graft is fixed in 60° of knee flexion with suture anchors.

RESULTS

Surgery for recurrent instability was performed in one case. There were no cases of infection, quadriceps tendon rupture, or patella fracture. At average follow-up of 29.2months (range, 24 to 38months), outcomes were good to excellent in 4/6 of cases. Kujala scores improved significantly from 33.3 (range, three to 58) preoperatively to 70.8 (range, 39 to 96) postoperatively (p<0.05). 5/6 patients reported being satisfied to completely satisfied with their result.

CONCLUSION

Patients undergoing bidirectional patellar stabilization with a single tendon graft showed improved postoperative functional scores. The technique is successful in reducing pain and restoring bidirectional patellar stability at 2-years follow-up.

LEVEL OF EVIDENCE

IV, retrospective case series.

Triple-Row Modification of the Suture-Bridge Technique for Arthroscopic Rotator Cuff Repair

Recent advances to improve outcomes in rotator cuff repair include using arthroscopic double-row suture-bridge techniques in an effort to reconstruct the rotator cuff footprint and improve fixation. However, when using this technique for larger tears, it can be difficult to get the lateral portion of the rotator cuff into an anatomic position. This report describes a triple-row modification of the suture-bridge technique that results in significantly more footprint contact area and contact pressure compared with the double-row and standard suture-bridge techniques. Maximizing the rotator cuff footprint contact area exposes more of the tendon to bone and may improve the healing potential.

Valgus Extension Overload: Arthroscopic Decompression in the Supine-Suspended Position

Elbow arthroscopy is a useful tool for managing diseases of the elbow, including valgus extension overload, when conservative treatments have failed. Arthroscopic access to the elbow in the supine-suspended position is simple and reproducible with the technique described in this report. Synovial tissue can be cleared, optimizing visualization of the anatomic structures in the elbow including the posterior ulnohumeral joint. This report describes, in detail, arthroscopy of the elbow in the supine-suspended position and basic principles for arthroscopic decompression of the posterior elbow for valgus extension overload.

Arthroscopic Scapulothoracic Decompression for Snapping Scapula Syndrome

Snapping scapula syndrome at the superomedial corner of the scapula can lead to significant shoulder dysfunction. Bursectomy with or without partial scapulectomy is currently the most beneficial primary method of treatment in patients in whom nonoperative therapy fails. Arthroscopic access to the scapulothoracic space is simple and reproducible with the technique described in this report. The bursal tissue can be cleared, optimizing visualization of the scapulothoracic space and the anatomic structures. Arthroscopic decompression of the scapulothoracic bursa and resection of the superomedial corner of the scapula are highlighted in a video example.

Arthroscopic irrigation and debridement in the treatment of septic arthritis after anterior cruciate ligament reconstruction

PURPOSE

To systematically review the literature and characterize the success and failure rates of arthroscopic irrigation and debridement (I & D) in the treatment of septic arthritis after anterior cruciate ligament (ACL) reconstructions. We also aimed to identify which variables affected the failure rate.

METHODS

Five databases (MEDLINE, Ovid, Medscape, Web of Science, and Google Scholar) were screened for clinical studies involving the treatment of septic arthritis after ACL reconstruction with arthroscopic I & D. A full-text review of eligible studies was conducted. Inclusion and exclusion criteria were applied to the searched studies. Failure of I & D was defined as the need for graft removal or revision ACL reconstructive surgery because of infection. Data from the selected studies were combined for statistical analyses to elucidate factors associated with the success or failure.

RESULTS

We identified 11 eligible studies involving 90 patients. These studies described the results of 90 arthroscopic I & D procedures with an overall success rate of 85.6%. Repeated I & D was necessary in 34.5% of patients. Removal of the graft with or without subsequent revision ACL reconstruction was reported in 13 (14.4%) cases. Statistical analysis showed that cases involving Staphylococcus aureus (P = .053), 2 or more I & D procedures (P = .029), and allografts (P < .0001) were at greater risk of failure.

CONCLUSIONS

Arthroscopic I & D with graft retention is an effective treatment for patients with septic arthritis after ACL reconstruction. Factors affecting the failure rate may include graft choice and organism virulence.

LEVEL OF EVIDENCE

Level IV, systematic review of Level IV studies.

Activation of the redox-regulated molecular chaperone Hsp33--a two-step mechanism

BACKGROUND

Hsp33 is a novel redox-regulated molecular chaperone. Hsp33 is present in the reducing environment of the cytosol and is, under normal conditions, inactive. The four highly conserved cysteines found in Hsp33 constitute a novel zinc binding motif. Upon exposure to oxidative stress, Hsp33's chaperone activity is turned on. This activation process is initiated by the formation of two intramolecular disulfide bonds. Recently, the 2.2 A crystal structure of Hsp33 has been solved, revealing that Hsp33 is present as a dimer in the structure (Vijayalakshmi et al., this issue, 367-375 [1]).

RESULTS

We show here that oxidized, highly active Hsp33 is a dimer in solution. In contrast, reduced and inactive Hsp33 is monomeric. The incubation of reduced Hsp33 in H(2)O(2) leads to the simultaneous formation of two intramolecular disulfide bonds and the concomitant release of zinc. This concentration-independent step is followed by a concentration-dependent association reaction. The dimerization of Hsp33 requires highly temperature-sensitive structural rearrangements. This allows Hsp33's activation process to be greatly accelerated at heat shock temperatures.

CONCLUSIONS

The regulation of Hsp33's chaperone function is highly sophisticated. On a transcriptional level, Hsp33 is under heat shock control. This increases the concentration of Hsp33 under heat and oxidative stress, a process that favors dimerization, a critical step in Hsp33's activation reaction. On a posttranslational level, Hsp33 is redox regulated. Dimerization of disulfide-bonded Hsp33 monomers leads to the formation of two extended, putative substrate binding sites. These sites might explain Hsp33's high and promiscuous affinity for unstructured protein folding intermediates.