Correlation of magnetic resonance imaging to arthroscopic findings of stability in juvenile osteochondritis dissecans.

PURPOSE: To determine the ability of magnetic resonance imaging (MRI) to characterize the stability of osteochondritis dissecans (OCD) fragments in juveniles. METHODS: Twenty-eight consecutive patients underwent surgery for OCD between 2004 and 2008. Of these, 23 patients had adequate preoperative imaging. There were 14 boys and 9 girls with a mean age of 12.9 years. Of the 23 lesions, 21 were located in the knee and 2 were located in the talus. On the basis of MRI, a single radiologist (1) indicated the presence or absence of 4 established magnetic resonance signs of instability, (2) classified each lesion according to a staging system for OCD stability, and (3) described the lesion as stable or unstable. These findings were compared with the arthroscopic findings. Arthroscopy was considered the gold standard for diagnosing fragment stability. RESULTS: Of the OCD lesions, 13 were found to be stable and 10 were found to be unstable. The final MRI impression was unstable in 21 patients and stable in 2 patients. This yielded a sensitivity of 100% and a specificity of 15% for diagnosing fragment instability. When 2 or more criteria were present, the specificity of MRI to classify lesion instability improved to 92%. The sensitivity, however, dropped to 50%. Concordance between arthroscopic stage and MRI stage was 30% (7 of 23). CONCLUSIONS: MRI predicted 21 of 23 lesions to be unstable, whereas arthroscopy found only 10 of these 23 lesions to be unstable. The most common pattern of false-positive findings involved lesions with an area of high signal intensity at the bone-fragment interface. MRI should not be used in isolation to determine lesion instability in young patients with juvenile OCD.

Arthroscopic rotator interval closure: effect of sutures on glenohumeral motion and anterior-posterior translation.

BACKGROUND: The effect of arthroscopic rotator interval closure on glenohumeral motion and translation is not well understood, nor is the ideal location or number of sutures required for closure. HYPOTHESIS: The number of arthroscopic rotator interval closure sutures and their placement will have a significant effect on glenohumeral range of motion and anterior-posterior translation. STUDY DESIGN: Controlled laboratory study. METHODS: Using a custom testing apparatus, the authors measured range of motion in 12 fresh-frozen cadaveric shoulders; anterior-posterior translation in adduction and neutral rotation was measured in 9. Specimens were initially tested without sutures and then tested after 3 interval closures using a random sequence of (1) an isolated medial suture at the level of the glenoid, (2) an isolated lateral suture 1 cm lateral to the glenoid, or (3) both sutures followed by removal of all sutures. RESULTS: Analysis of variance demonstrated that interval closure had a significant effect on decreasing flexion (mean, 6 degrees), external rotation (mean, 10 degrees), and anterior translation (mean, 3 mm) of the adducted shoulder. There was no significant difference between the 3 interval closures in any of the tests. CONCLUSION: Arthroscopic interval closure produced significant decreases in range of motion and anterior-posterior translation. The effects of single lateral or medial suture closures were similar to the use of 2 sutures. CLINICAL RELEVANCE: This study suggests that the initial effect of arthroscopic rotator interval closure on anterior translation of the shoulder will be similar whether 1 or 2 sutures are used. In vivo studies are necessary to determine if the effect of these 2 methods would be the same over time.

The effect of interference screw diameter on soft tissue graft fixation.

Tibial fixation of soft-tissue grafts is a weak link in anterior cruciate ligament reconstruction. Previous studies have examined varying interference screw lengths, screw types and tunnel sizes as means to improve graft fixation. We hypothesized that increasing interference screw diameter would significantly increase the maximum load to failure of the graft and decrease the graft's initial slippage. Seventy tibialis anterior and tibialis posterior tendons were divided, looped, trimmed, and sutured to simulate 4-strand hamstring grafts. These grafts were then inserted into composite bone blocks having pre-drilled 8 mm holes and fixed with 8 mm, 9 mm, 10 mm, 11 mm, or 12 mm interference screws. Fourteen grafts were tested for each screw size. The graft was first cyclically loaded from 50 N to 250 N at 0.3 Hz for 100 cycles to measure graft slippage. The graft was then tested to failure at 0.5 mm/sec to determine the maximum load to failure and mode of failure. Graft slippage was not affected by screw diameter. Maximum load to failure increased with increasing screw diameter up to 11 mm; 11 mm screw fixation was 20% stronger than 8 mm screw fixation. In this model, no increase in graft fixation was seen in by increasing interference screw diameter beyond 3 mm of the tunnel diameter.

Suture versus screw fixation of displaced tibial eminence fractures: a biomechanical comparison.

PURPOSE: Classification and treatment of tibial eminence fractures are determined by the degree of fragment displacement. A variety of surgical procedures have been proposed to stabilize displaced fractures using both open and arthroscopic techniques. Two common fixation techniques involve use of cannulated screws and sutures tied over an anterior tibial bone bridge. We are unaware of any biomechanical studies that have compared the strength of various techniques of fixation. TYPE OF STUDY: Biomechanical study in a cadaveric model. METHODS: Seven matched pairs of fresh-frozen human cadaveric knees were stripped of all soft tissue except the anterior cruciate ligament (ACL). Simulated type III tibial eminence fractures were created using an osteotome. Fragments of each matched pair were randomized to fixation with either a single 4-mm cannulated cancellous screw with a washer or an arthroscopic suture technique using 3 No. 2 Fiberwire sutures (Arthrex, Naples, FL) passed through the tibial base of the ACL and tied over bone tunnels on the anterior tibial cortex. Specimens were then loaded with a constant load rate of 20 mm/min, and load-deformation curves were generated. The ultimate strength and stiffness were computed for each curve. The failure mode for each test was observed. A paired 2-tailed t test was used to determine the statistically significant difference between the two methods. RESULTS: Specimens fixed with Fiberwire had a mean ultimate strength of 319 N with a standard deviation of 125 N. Those fixed with cannulated screws had a mean ultimate strength of 125 N with a standard deviation of 74 N. This difference was statistically significant (P = .0038). There was no significant difference between the mean stiffness of Fiberwire constructs (63 N; SD, 50 N) and the mean stiffness of the cannulated screw constructs (20 N; SD, 32 N). The failure modes of the Fiberwire constructs included 1 ACL failure, 3 failures of suture cutting through the anterior tibial cortex, and 3 of suture cutting through the tibial eminence fragment. The single mode of failure for the cannulated screw constructs was screw pullout of cancellous bone. CONCLUSIONS: The initial ultimate strength of Fiberwire fixation of tibial eminence fractures in these specimens was significantly stronger than that of cannulated screw fixation. CLINICAL RELEVANCE: It appears that Fiberwire fixation of eminence fractures provides biomechanical advantages over cannulated screw fixation and may influence the type of treatment one chooses for patients with tibial eminence fractures.

Assessment of clavicular translation after arthroscopic Mumford procedure: direct versus indirect resection--a cadaveric study.

PURPOSE: To compare the horizontal stability of the distal clavicle following arthroscopic resection of its lateral end by direct and indirect techniques. TYPE OF STUDY: Biomechanical test of cadaveric specimens. METHODS: We performed arthroscopic distal clavicle resection on 12 fresh-frozen human cadaveric shoulders using direct (group 1, n = 6) or indirect (group 2, n = 6) approaches. In both groups 5 mm of distal clavicle were resected using an arthroscopic burr. The specimens were mounted on a materials testing device that allowed translation of the clavicle along the anteroposterior axis. The degree of posterior translation was measured from maximum anterior displacement of the clavicle. RESULTS: Mean posterior translation was 19.4 mm (range, 18 to 23 mm; SD, 2.2) and 21.3 mm (range, 18 to 25 mm; SD, 3.1) for groups 1 and 2, respectively. This difference was not statistically significant ( P = .27). CONCLUSIONS: This study suggests that there is no significant difference in anteroposterior stability of the clavicle following arthroscopic distal clavicle resection with either a direct or indirect approach. CLINICAL RELEVANCE: Clinically, this study addresses concerns about increased potential instability associated with the indirect technique of distal clavicle resection. From a biomechanical standpoint, based on this study, there is no concern for increased instability with the indirect technique of distal clavicle resection compared to a direct technique.

The effects of radiofrequency bipolar thermal energy on human meniscal tissue.

This study performed the first in vitro histological analysis of the effects of bipolar thermal energy on human meniscal tissue. Sixteen fresh human menisci were mounted on a cutting block and placed in a water bath simulating an arthroscopic environment. Each specimen was divided into four sections and randomized to one of four treatment options: 1. thermal ablation with a bipolar multielectrode 3 mm Covac wand (power 3 setting); 2. thermal ablation with a bipolar multielectrode 3 mm Covac wand (power setting 7); 3. resection with a scalpel blade; and 4. resection with a motorized 4.5 full-radius resector. Six micron sections were cut and stained with Hematoxylin and Eosin and Masson's trichrome stain. Menisci were evaluated for the contour of the cut edge: straight, jagged, frayed, or combined. The zone of thermal necrosis and zone of thermal alteration were determined by examining the differential staining of the connective tissue and measuring the affected area. Menisci treated with the bipolar thermal probe were noted to have a smoother contoured edge in comparison to motorized cutters. The zone of thermal penetration for the Arthrocare power setting 3 averaged 0.18 mm (range: 0.09 to 0.20; SD 0.04) and for Arthrocare power setting 7 averaged 0.33 mm (range: 0.26 to 0.36; SD 0.03). The difference in thermal penetration between Arthrocare power settings 3 and 7 was 0.15 mm. This was statistically significant at p < 0.0001 (95% CI: 0.11 to 0.19 mm). The zone of thermal penetration was non-existent for the shaver and scalpel groups. This study provides the first histological description of the effects of bipolar radiofrequency energy on meniscal tissue. It demonstrates that there is intra-substance thermal penetration and alteration of the meniscal tissue. Its clinical significance is unclear and further in vivo studies are needed to address its clinical applicability.