C. Benjamin Ma

Current trends in anterior cruciate ligament reconstruction. Part 1 : Biology and biomechanics of reconstruction

With todays increasing emphasis on sporting activities, the incidence of anterior cruciate ligament injuries has also increased. Epidemiologic studies estimate that the prevalence of anterior cruciate ligament injuries is about 1 per 3000 Americans. Management of these injuries has evolved from nonoperative treatment to extracapsular augmentation and primary ligament repair to anterior cruciate ligament reconstruction. Treatment of these injuries has significantly improved over the last few decades with the application of knowledge gained from both basic science and clinical research. This article is composed of two parts. The first part reviews the biology and biomechanics of the injured anterior cruciate ligament and the basic science of reconstruction. In the second part, to be published later, current operative concepts of reconstruction, as well as clinical correlations, are reviewed. Summarizing the latest information on basic scientific as well as clinical studies regarding the anterior cruciate ligament, this article intends to demonstrate the correlation between the application of basic science knowledge and improvement of clinical outcomes.

Biomechanical Evaluation of Arthroscopic Rotator Cuff Repairs: Double-Row Compared with Single-Row Fixation

BACKGROUND Recent studies have shown that arthroscopic rotator cuff repairs can have higher rates of failure than do open repairs. Current methods of rotator cuff repair have been limited to single-row fixation of simple and horizontal stitches, which is very different from open repairs. The objective of this study was to compare the initial cyclic loading and load-to-failure properties of double-row fixation with those of three commonly used single-row techniques. METHODS Ten paired human supraspinatus tendons were split in half, yielding four tendons per cadaver. The bone mineral content at the greater tuberosity was assessed. Four stitch configurations (two-simple, massive cuff, arthroscopic Mason-Allen, and double-row fixation) were randomized and tested on each set of tendons. Specimens were cyclically loaded between 5 and 100 N at 0.25 Hz for fifty cycles and then loaded to failure under displacement control at 1 mm/sec. Conditioning elongation, peak-to-peak elongation, ultimate tensile load, and stiffness were measured with use of a three-dimensional tracking system and compared, and the failure type (suture or anchor pull-out) was recorded. RESULTS No significant differences were found among the stitches with respect to conditioning elongation. The mean peak-to-peak elongation (and standard error of the mean) was significantly lower for the massive cuff (1.1 +/- 0.1 mm) and double-row stitches (1.1 +/- 0.1 mm) than for the arthroscopic Mason-Allen stitch (1.5 +/- 0.2 mm) (p < 0.05). The ultimate tensile load was significantly higher for double-row fixation (287 +/- 24 N) than for all of the single-row fixations (p < 0.05). Additionally, the massive cuff stitch (250 +/- 21 N) was found to have a significantly higher ultimate tensile load than the two-simple (191 +/- 18 N) and arthroscopic Mason-Allen (212 +/- 21 N) stitches (p < 0.05). No significant differences in stiffness were found among the stitches. Failure mechanisms were similar for all stitches. Rotator cuff repairs in the anterior half of the greater tuberosity had a significantly lower peak-to-peak elongation and higher ultimate tensile strength than did repairs on the posterior half. CONCLUSIONS In this in vitro cadaver study, double-row fixation had a significantly higher ultimate tensile load than the three types of single-row fixation stitches. Of the single-row fixations, the massive cuff stitch had cyclic and load-to-failure characteristics similar to the double-row fixation. Anterior repairs of the supraspinatus tendon had significantly stronger biomechanical behavior than posterior repairs.

Biomechanical evaluation of arthroscopic rotator cuff stitches

BACKGROUND The suture configurations in arthroscopic rotator cuff repairs have been limited to simple and horizontal stitches. Recent objective evaluations have demonstrated high failure rates of arthroscopic repairs of rotator cuff tears. A novel stitch for arthroscopic repair of the rotator cuff, the massive cuff stitch, was developed to increase the strength of the suture-tendon interface. The goal of this study was to determine the biomechanical properties of the massive cuff stitch and to compare it with other stitches commonly used for rotator cuff repair. METHODS Eight pairs of sheep infraspinatus tendons were harvested and split in half to yield a set of four tendon specimens from each animal. Four stitch configurations (simple, horizontal, massive cuff, and modified Mason-Allen) were randomized and biomechanically tested in each set of tendon specimens. Each specimen was first cyclically loaded on an MTS uniaxial load frame under force control from 5 to 30 N at 0.25 Hz for twenty cycles. Each specimen was then loaded to failure under displacement control at a rate of 1 mm/sec. Cyclic elongation, peak-to-peak displacement, ultimate tensile load, and stiffness were measured with use of an optical motion analysis system and load-cell output. The type of failure (suture breakage or pull-out) was also recorded. A repeated-measures analysis of variance was performed on the results, with the alpha level of significance set at p < 0.05. RESULTS There was no difference in cyclic elongation or peak-to-peak displacement among the four stitches. Ultimate tensile load was significantly higher (p < 0.05) for the massive cuff stitch (233 +/- 40 N) and the modified Mason-Allen stitch (246 +/- 40 N) than it was for either the simple stitch (72 +/- 18 N) or the horizontal stitch (77 +/- 15 N). There was no significant difference in the ultimate load between the massive cuff and modified Mason-Allen stitches. There was also no difference in stiffness among the four stitches. The simple and horizontal stitches failed by tissue pull-out, whereas the massive cuff and Mason-Allen stitches failed by a mixture of suture breakage and pull-out. CONCLUSIONS The massive cuff stitch provides strength comparable with that of the modified Mason-Allen stitch commonly used in open rotator cuff repair. The ultimate tensile load before failure of the massive cuff stitch was significantly higher (p < 0.05) than that of the simple and horizontal stitches.

T1rho, T2 and focal knee cartilage abnormalities in physically active and sedentary healthy subjects versus early OA patients—a 3.0-Tesla MRI study

Abstract(1) To assess the degree of focal cartilage abnormalities in physically active and sedentary healthy subjects as well as in patients with early osteoarthritis (OA). (2) To determine the diagnostic value of T2 and T1rho measurements in identifying asymptomatic physically active subjects with focal cartilage lesions. Thirteen asymptomatic physically active subjects, 7 asymptomatic sedentary subjects, and 17 patients with mild OA underwent 3.0-T MRI of the knee joint. T1rho and T2 values, cartilage volume and thickness, as well as the WORMS scores were obtained. Nine out of 13 active healthy subjects had focal cartilage abnormalities. T1rho and T2 values in active subjects with and without focal cartilage abnormalities differed significantly (p < 0.05). T1rho and T2 values were significantly higher (p < 0.05) in early OA patients compared to healthy subjects. T1rho measurements were superior to T2 in differentiating OA patients from healthy subjects, yet T1rho was moderately age-dependent. (1) Active subjects showed a high prevalence of focal cartilage abnormalities and (2) active subjects with and without focal cartilage abnormalities had different T1rho and T2 composition of cartilage. Thus, T1rho and T2 could be a parameter suited to identify active healthy subjects at higher risk for developing cartilage pathology.

Hamstring graft motion in the femoral bone tunnel when using titanium button/ polyester tape fixation

Abstract The objective of this study was to determine the relative motion of a quadruple hamstring graft within the femoral bone tunnel (graft-tunnel motion) under tensile loading. Six graft constructs were prepared from the semitendinosus and gracilis tendons of human cadavers and were fixed with a titanium button and polyester tape within a bone tunnel in a cadaveric femur. Three different lengths of polyester tape (15, 25, and 35 mm loops) were evaluated. The femur was held stationary and uniaxial tensile loads were applied to the distal end of the graft using a materials testing machine. Each construct was subjected to loading for ten cycles with upper limits of 50 N, 100 N, 200 N and 300 N. Graft-tunnel motion was then determined using the distances between reflective tape markers placed on the hamstring graft and at the entrance to the femoral bone tunnel, which were tracked with a high-resolution video system. Graft-tunnel motion was found to range from 0.7 ± 0.2 mm to 3.3 ± 0.2 mm, and significant increases in graft-tunnel motion were observed with increasing tensile loads (P < 0.05). Shorter tape length (15 mm) resulted in significantly less motion when compared to longer tape length (35 mm) (P < 0.05). We conclude that graft-tunnel motion is significant and should be considered when using this fixation technique. Early stress on the graft, as seen in postoperative rehabilitation exercises and athletic activities, may cause large graft-tunnel motion before graft incorporation is complete. A shorter distance between the tendon tissue and the titanium button is recommended to minimize the amount of graft-tunnel motion. Alternative fixation materials to polyester tape, or different fixation techniques, need to be developed such that graft-tunnel motion can be reduced. Further studies are needed to evaluate the effect of graft-tunnel motion on graft incorporation in the bone tunnel.

A Multidisciplinary Study of the Healing of an Intraarticular Anterior Cruciate Ligament Graft in a Goat Model

We evaluated knee function, tensile properties, and histologic appearance of a healing intraarticular bone-patellar tendon-bone autograft after anterior cruciate ligament reconstruction in a goat model. The patellar tendon graft was fixed such that both bone-to-bone (femoral tunnel) and bone-to-tendon (tibial tunnel) healing could be studied. The total anteroposterior translation significantly increased from 3 to 6 weeks, ranging from increases of 28.8% to 46.7%. In situ forces in the replacement graft decreased as much as 22.2% at 6 weeks. Conversely, tensile properties of the femur-anterior cruciate ligament graft-tibia complex did not change significantly from 3 to 6 weeks. However, the mode of failure changed from the graft pulling out of the tibial tunnel at 3 weeks to a mix of midsubstance failures (N = 2) and pullouts (N = 5) at 6 weeks. Histologic evaluations revealed progressive and complete incorporation of the bone block in the femoral tunnel, but only partial incorporation of the tendinous part of the graft in the tibial tunnel. The differences demonstrated at 3 and 6 weeks may be a result of the remodeling process of the midsubstance of the graft as the interfaces within the osseous tunnels mature.

In vivo 3T spiral imaging based multi‐slice T1ρ mapping of knee cartilage in osteoarthritis

T1ρ describes the spin‐lattice relaxation in the rotating frame and has been proposed for detecting damage to the cartilage collagen‐proteoglycan matrix in osteoarthritis. In this study, a multi‐slice T1ρ imaging method for knee cartilage was developed using spin‐lock techniques and a spiral imaging sequence. The adverse effect of T1 regrowth during the multi‐slice acquisition was eliminated by RF cycling. Agarose phantoms with different concentrations, 10 healthy volunteers, and 9 osteoarthritis patients were scanned at 3T. T1ρ values decreased as agarose concentration increased. T1ρ values obtained with imaging methods were compared with those obtained with spectroscopic methods. T1ρ values obtained during multi‐slice acquisition were validated with those obtained in a single slice acquisition. Reproducibility was assessed using the average coefficient of variation of median T1ρ, which was 0.68% in phantoms and 4.8% in healthy volunteers. There was a significant difference (P = 0.002) in the average T1ρ within patellar and femoral cartilage between controls (45.04 ± 2.59 ms) and osteoarthritis patients (53.06 ± 4.60 ms). A significant correlation was found between T1ρ and T2; however, the difference of T2 was not significant between controls and osteoarthritis patients. The results suggest that T1ρ relaxation times may be a promising clinical tool for osteoarthritis detection and treatment monitoring. Magn Reson Med, 2005.

Cartilage in anterior cruciate ligament-reconstructed knees: MR imaging T1{rho} and T2--initial experience with 1-year follow-up.

PURPOSE To longitudinally evaluate cartilage matrix changes by using magnetic resonance (MR) imaging T1(ρ) (T1 relaxation time in rotating frame) and T2 quantification and to study the relationship between meniscal damage and cartilage degeneration in anterior cruciate ligament (ACL)-reconstructed knees. MATERIALS AND METHODS This was an institutional review board-approved, HIPAA-compliant study. Informed consent was obtained. Twelve patients with acute ACL injuries were imaged with 3.0-T MR imaging at baseline (after injury and prior to ACL reconstruction) and 1 year after ACL reconstruction. Ten age-matched healthy subjects were studied as controls. Cartilage T1(ρ) and T2 were quantified in full thickness, superficial, and deep layers of defined subcompartments at baseline and follow-up in ACL-injured knees and were compared with measures acquired in matched regions of control knees. Meniscal lesions were graded by using modified subscores of the Whole-Organ Magnetic Resonance Imaging Score system. RESULTS T1(ρ) values of the posterolateral tibial cartilage in ACL-injured knees were significantly elevated at baseline compared with T1(ρ)values of control knees and were not fully recovered at 1-year follow-up. T1(ρ) values of weight-bearing medial femorotibial cartilage in ACL-injured knees were significantly elevated at 1-year follow-up compared with those of control knees. No significant differences in T2 values between ACL-injured and control knees were found. Patients with lesions in the posterior horn of the medial meniscus showed a greater increase of T1(ρ) and T2 from baseline to follow-up in adjacent cartilage than patients without lesions in the medial meniscus. CONCLUSION Quantitative MR imaging T1(ρ) and T2 enable detection of changes in the cartilage matrix of ACL-reconstructed knees as early as 1 year after ACL reconstruction.

Effectiveness of physical therapy in treating atraumatic full-thickness rotator cuff tears: a multicenter prospective cohort study

PURPOSE To assess the effectiveness of a specific nonoperative physical therapy program in treating atraumatic full-thickness rotator cuff tears using a multicenter prospective cohort study design. MATERIALS AND METHODS Patients with atraumatic full-thickness rotator cuff tears who consented to enroll provided data via questionnaire on demographics, symptom characteristics, comorbidities, willingness to undergo surgery, and patient-related outcome assessments (Short Form 12 score, American Shoulder and Elbow Surgeons score, Western Ontario Rotator Cuff score, Single Assessment Numeric Evaluation score, and Shoulder Activity Scale). Physicians recorded physical examination and imaging data. Patients began a physical therapy program developed from a systematic review of the literature and returned for evaluation at 6 and 12 weeks. At those visits, patients could choose 1 of 3 courses: (1) cured (no formal follow-up scheduled), (2) improved (continue therapy with scheduled reassessment in 6 weeks), or (3) no better (surgery offered). Patients were contacted by telephone at 1 and 2 years to determine whether they had undergone surgery since their last visit. A Wilcoxon signed rank test with continuity correction was used to compare initial, 6-week, and 12-week outcome scores. RESULTS The cohort consists of 452 patients. Patient-reported outcomes improved significantly at 6 and 12 weeks. Patients elected to undergo surgery less than 25% of the time. Patients who decided to have surgery generally did so between 6 and 12 weeks, and few had surgery between 3 and 24 months. CONCLUSION Nonoperative treatment using this physical therapy protocol is effective for treating atraumatic full-thickness rotator cuff tears in approximately 75% of patients followed up for 2 years.

Interobserver Agreement in the Classification of Rotator Cuff Tears Using Magnetic Resonance Imaging

Background Although magnetic resonance imaging (MRI) is a standard method of assessing the extent and features of rotator cuff disease, the authors are not aware of any studies that have assessed the interobserver agreement among orthopaedic surgeons reviewing MRI scans for rotator cuff disease. Hypothesis Fellowship-trained orthopaedic shoulder surgeons will have good interobserver agreement in predicting the more salient features of rotator cuff disease such as tear type (full thickness versus partial thickness), tear size, and number of tendons involved but only fair agreement with more complex features such as muscle volume, fat content, and the grade of partial-thickness cuff tears. Study Design Cohort study (diagnosis); Level of evidence, 3. Methods Ten fellowship-trained orthopaedic surgery shoulder specialists reviewed 27 MRI scans of 27 shoulders from patients with surgically confirmed rotator cuff disease. The ability to interpret full-thickness versus partial-thickness tears, acromion type, acromioclavicular joint spurs or signal changes, biceps lesions, size and grade of partial-thickness tears, acromiohumeral distance, number of tendons involved and amount of retraction for full-thickness tears, size of full-thickness tears, and individual muscle fatty infiltration and atrophy were assessed. Surgeons completed a standard evaluation form for each MRI scan. Interobserver agreement was determined and a kappa level was derived. Results Interobserver agreement was highest (>80%) for predicting full- versus partial-thickness tears of the rotator cuff, and for quantity of the teres minor tendon. Agreement was slightly less (>70%) for detecting signal in the acromioclavicular joint, the side of the partial-thickness tear, the number of tendons involved in a full-thickness tear, and the quantity of the subscapularis and infraspinatus muscle bellies. Agreement was less yet (60%) for detecting the presence of spurs at the acromioclavicular joint, a tear of the long head of the biceps tendon, amount of retraction of a full-thickness tear, and the quantity of the supraspinatus. The best kappa statistics were found for detecting the difference between a full- and partial-thickness rotator cuff tear (0.77), and for the number of tendons involved for full-thickness tears (0.55). Kappa for predicting the involved side of a partial-thickness tear was 0.44; for predicting the grade of a partial-thickness tear, it was −0.11. Conclusions Fellowship-trained, experienced orthopaedic surgeons had good agreement for predicting full-thickness rotator cuff tears and the number of tendons involved and moderate agreement in predicting the involved side of a partial-thickness rotator cuff tear, but poor agreement in predicting the grade of a partial-thickness tear.