Scott G. Kaar

EFFECT OF HUMERAL HEAD DEFECT SIZE ON GLENOHUMERAL STABILITY: A CADAVERIC STUDY OF SIMULATED HILL-SACHS DEFECTS

Background Hill-Sachs lesions are often present with recurrent shoulder instability and may be a cause of failed Bankart repair. Hypothesis Glenohumeral joint stability decreases with increasingly larger humeral head defects. Study Design Descriptive laboratory study. Methods Humeral head defects, 1/8, 3/8, 5/8, and 7/8 of the humeral head radius, were created in 8 human cadaveric shoulders, simulating Hill-Sachs defects. Testing positions included 45° and 90° of abduction and 40° of internal rotation, neutral, and 40° of external rotation. Testing occurred at each defect size sequentially from smallest to largest for all abduction and rotation combinations. The humeral head was translated at 0.5 mm/s 45° anteroinferiorly to the horizontal glenoid axis until dislocation. Distance to dislocation, defined as humeral head translation until it began to subluxate, was the primary outcome measure. Results Significant factors by ANOVA were rotation (P < .001) and defect size (P < .001). There was no difference for the 2 abduction angles. External rotation of 40° significantly reduced distance to dislocation compared with neutral and 40° internal rotation (P < .001). Osteotomies of 5/8 and 7/8 radius significantly decreased distance to dislocation over the intact state (P = .009 and P < .001, respectively). Post hoc analysis determined significant differences for the rotational positions. Decreased distance to dislocation occurred at 5/8 radius osteotomy at 40° external rotation with 90° of abduction (P = .008). For the 7/8 radius osteotomy at 90° abduction, there was a decreased distance to dislocation for neutral and 40° external rotation (P < .001); at 45° abduction, there was a decreased distance to dislocation at 40° external rotation (P < .001). With the humerus internally rotated, there was no significant change in distance to dislocation. Conclusion Glenohumeral stability decreases at a 5/8 radius defect in external rotation and abduction. At 7/8 radius, there was a further decrease in stability at neutral and external rotation. Clinical Relevance Defects of 5/8 the humeral head radius may require treatment to decrease the failure rate of shoulder instability repair.

Comparison Between Rigid and Flexible Systems for Drilling the Femoral Tunnel Through an Anteromedial Portal in Anterior Cruciate Ligament Reconstruction

PURPOSE The purpose of this study was to compare the differences in femoral tunnel length and distance to the lateral anatomic structures when using standard and flexible guide pins for anterior cruciate ligament (ACL) femoral tunnel drilling through a medial portal. METHODS Using a medial arthroscopic portal in 10 cadaveric knees, we sequentially drilled straight and flexible guide pins into the center of the ACL femoral footprint using the same starting point. We recorded the interosseous length and distances to the peroneal nerve and the femoral origin of the lateral collateral ligament (LCL) for each pin. RESULTS The mean interosseous length was 43.5 mm for the flexible pin and 37.1 mm for the straight pin (P = .01). The mean distance to the peroneal nerve was 42.3 mm for the flexible pin and 37.8 mm for the straight pin (P = .33). The mean distance to the femoral origin of the LCL was 26.1 mm for the flexible pin and 13.4 mm for the straight pin (P = .003). CONCLUSIONS The use of commercially available flexible reamers and 42 degrees femoral guides results in longer femoral interosseous tunnel length than can be achieved with a straight guide pin. Femoral interosseous length consistently of 40 mm can be achieved with this technique and cannot be replicated with a rigid straight pin. This is advantageous for femoral tunnel drilling in an anatomic ACL reconstruction that uses suspensory fixation devices. There is minimal risk to the peroneal nerve and the femoral origin of the LCL unless lateral femoral wall blowout occurs. CLINICAL RELEVANCE Flexible pins allow longer femoral tunnels and safer distances from the LCL by use of a medial portal technique.

Latissimus Dorsi and Teres Major Tears in Professional Baseball Pitchers: A Case Series

Background Latissimus dorsi and teres major tendon tears are uncommon injuries. Only a few case reports exist, mainly in high-level athletes. Purpose To describe a series of latissimus dorsi and teres major tendon tears in professional baseball pitchers. Study Design Case series; Level of evidence, 4. Methods Injury data from 3 Major League Baseball clubs were collected over a total of 10 seasons. Any baseball player who sustained an injury to either the latissimus dorsi or teres major identified on magnetic resonance imaging (MRI) was included. All injured players were treated nonoperatively with a goal of returning to full velocity throwing at 3 months from the time of injury. Results Ten players sustained injuries to the latissimus dorsi and/or the teres major during pitching. The MRI findings documented 5 isolated latissimus dorsi tears, 4 isolated teres major tears, and 1 combined injury. All athletes returned to pitching, and all but 1 player returned to baseball at the same level of competition in the same season. Nine of 10 players returned at 3 months from the time of their injury. One recurrence was seen 6 months after returning to throwing; however, this healed with further nonoperative treatment, and the player returned to competition at the same level 6 weeks later. One player had continued shoulder symptoms and retired at the end of the season. Conclusion Although uncommon, tears of the latissimus dorsi and teres major occur in professional baseball players. Acute injuries are demonstrated on standard shoulder MRI, although larger field-of-view images are required to accurately assess the injury. Most heal successfully with nonoperative treatment, and most players are able to return to the same level of competition in 3 months.

Relationship of cortical thickness of the proximal humerus and pullout strength of a locked plate and screw construct.

Background: No study to date has evaluated cortical thickness as it relates to locking plate failure or screw pullout in the proximal humerus. The purpose of this study is to determine the relationship between proximal humerus cortical thickness and locked plate hardware failure in a cadaveric proximal humerus fracture model. Methods: Twelve humerus specimens were placed into two groups based on the proximal humerus cortical thickness on an anteroposterior radiograph: less than 4 mm and greater than 4 mm. The specimens were plated with a six-hole proximal humerus locking plate and a 15-mm resection osteotomy at the surgical neck was performed. The specimens were tested in a materials testing machine at a displacement of 5 mm/min to failure. Results: Load at failure, stiffness, maximum load, failure, and fracture gap closure were all statistically similar (P > 0.05) between the groups. Conclusion: Our biomechanical study used modern locked plate–screw construct fixation of a simulated two-part proximal humerus fracture. The mechanical strength was unaffected based on a threshold combined proximal humerus cortical thickness of 4 mm.

Is the Marx Activity Scale Reliable in Patients Younger Than 18 Years

Background: There is no baseline activity scale yet validated in pediatric patients. The Marx and Tegner scales have been validated in adult patients only. The Tegner scale involves questions not pertinent to children, such as their work activity. The Marx scale is simple, and all its questions can be related to athletic activities. Hypothesis: The Marx scale is reliable for use in a pediatric population. Study Design: Cohort study. Level of Evidence: Level 2. Methods: Patients younger than 18 years were given the Marx activity scale in clinic and again 3 weeks later. The patients were divided into 3 groups, of at least 50 patients each, based on presenting diagnosis: knee injury, lower extremity (non-knee) injury, and upper extremity injury. Test-retest reliability was determined for the overall scores and the individual questions. Differences in scores were also compared based on age (<14 vs ≥14 years). Results: A total of 162 patients (mean age, 14.4 years; range, 8-17 years) were included. The Marx scale had a high intraclass correlation coefficient (ICC) overall as well as for each of its 4 questions. Both older and younger patients had ICCs >0.80, though the older group generally had higher scores. The mean score was 13.55 (out of 16), and 50.6% scored the maximum; only 1.9% scored the minimum. Mean scores for the knee, lower extremity, and upper extremity groups were 13.71 (SD, 3.70), 13.22 (SD, 4.18), and 13.68 (SD, 3.33), respectively (P > 0.05). There also was no difference in total score based on age (P = 0.88). Conclusion: The Marx activity scale is reliable in patients younger than 18 years with injuries to the knee and lower extremities, though the scale was less reliable in patients younger than 14 years. There is a significant ceiling effect present, which limits its overall usefulness. Clinical Relevance: Although there is no other current substitute, the Marx activity scale is not an ideal measurement of younger patients’ baseline activity levels.

No Contribution of Tension-Reducing Rotator Cuff Sutures on Locking Plate Fixation in a 2-Part Proximal Humerus Fracture Model.

Objectives: Varus failure is a well-known complication of open reduction internal fixation of proximal humeral fractures. The addition of tension-reducing sutures from the plate to the rotator cuff may attenuate the deforming forces of the rotator cuff resulting in decreased varus failure. In this study, we investigate the biomechanical contributions of tension-reducing sutures to a locked plate construct in a 2-part proximal humerus fracture model. Methods: Two fixation techniques were tested in 12 matched fresh frozen humeri in which standard 2-part fractures of the surgical neck were created with a gap simulating surgical neck medial comminution. In group 1, fractures were fixed with a standard proximal humerus locking plate. In group 2, the plate fixation was similar, and additionally, tension-reducing sutures were applied from the plate to the rotator cuff. Active abduction was simulated for 400 cycles with force applied through the rotator cuff tendons. Intercyclic fracture motion, change in displacement, and load to failure were recorded. Results: The addition of tension-reducing sutures did not lead to significant differences in intercyclic fracture motion. The mean change in displacement and load to failure were similar in both groups. Failure typically occurred in both groups at the rotator cuff testing clamp interface. Conclusions: Tension-relieving rotator cuff sutures added to locking plate fixation did not lead to a change in fracture gap with cyclic loading or an increase in ultimate failure load in a 2-part surgical neck proximal humerus fracture model without medial support.

Biomechanical contribution of tension-reducing rotator cuff sutures in 3 part proximal humerus fractures:

Objectives: Using a cadaveric 3-part fracture model and cyclic loading protocol, our study objectives were to quantify the stabilizing effect of tension-reducing rotator cuff sutures in terms of fracture displacement across the surgical neck and greater tuberosity compared with a control group in which no sutures were used. Methods: Six matched pairs of fresh frozen specimens underwent a standardized, 3-part, proximal humerus fracture and were split into 2 groups. The control group had the fracture fixed with a plate and screw construct only while the experimental group had additional suture fixation through the plate to each rotator cuff tendon. Active abduction through the rotator cuff was simulated for 100, 200, 300, and 400 cycles and to failure at 1000 N. A Mann–Whitney U test compared cyclic displacement of the greater tuberosity and surgical neck fracture gaps and load to failure between the 2 groups. Results: There was no significant difference (P > 0.05) in fracture gap between fixation methods at the surgical neck at 100 (P = 0.13), 200 (P = 0.07), 300 (P = 0.49), and 400 (P = 0.07) cycles. There was no significant difference (P > 0.05) between fixation methods in the fracture gap at the greater tuberosity at 100 (P = 0.39), 200 (P = 1.00), 300 (P = 0.31), and 400 (P = 0.59) cycles. There was no significant difference (P > 0.5) at 1000 N at the surgical neck (P = 0.70) or the greater tuberosity (P = 0.39). Conclusions: Tension-relieving rotator cuff sutures do not add stability to the repair of 3-part proximal humerus fractures. Varus collapse and greater tuberosity displacement are common complications associated with 3-part fractures. No mechanical data exist to demonstrate benefit of adding suture to a plate and screw construct for limiting fracture displacement.

Anterior Cruciate Ligament Graft Isometry Is Affected by the Orientation of the Femoral Tunnel

PURPOSE The purpose of this study was to compare anterior cruciate ligament (ACL) graft length and tension throughout knee range of motion with transtibial, anteromedial (AM) portal, and all-epiphyseal drilling techniques with suspensory and apical femoral fixation. METHODS The three different femoral tunnel drilling techniques using the same intra-articular starting point within the center of the femoral footprint were performed on fresh-frozen cadaveric specimens. All groups underwent standard tibial drilling in the center of the ACL tibial footprint. FiberWire (Arthrex Inc., Naples, FL) was used to simulate anatomic single bundle reconstructions. Changes in graft length and tension were measured at knee flexion angles of 0, 30, 60, 90, 120, and 135 degrees. RESULTS Graft length and tension decreased from 0 through 60 degrees and subsequently increased from 90 to 135 degrees for all groups. The transtibial, AM portal suspensory, and apical fixation groups were similar. However, the all-epiphyseal tunnel with suspensory fixation had a significantly increased change in length (90, 120, and 135 degrees) and tension (120 and 135 degrees). CONCLUSION Transtibial and AM portal suspensory fixation and apical fixation demonstrate similar changes in length and tension throughout knee range of motion. The all-epiphyseal tunnel with suspensory fixation was associated with greater length and tension changes at higher degrees of knee flexion. All techniques demonstrated decreased graft length and tension with knee flexion to 60 degrees after which they increased with further knee flexion. CLINICAL RELEVANCE ACL graft length and tension change throughout knee range of motion and also depend on femoral tunnel orientation and fixation type. The use of an all-epiphyseal tunnel with suspensory fixation should be studied further for evidence of graft elongation.

What Effect Does Anterior Cruciate Ligament Tibial Guide Orientation Have on Tibial Tunnel Length

PURPOSE To evaluate the effects of alteration in tibial guide pin insertion angle and external starting point on tibial tunnel length for anterior cruciate ligament (ACL) reconstruction. METHODS Ten cadaveric tibial specimens were used. One pin was placed at each of variable insertion angles (55°, 50°, and 45°) of the tibial targeting device aimed at the center of the tibial ACL footprint. These 3 pins started externally along the anterior border of the superficial medial collateral ligament. A fourth pin at 50° was placed at a different external tibial starting point 1.5 cm anterior to the anterior border of the superficial medial collateral ligament. The intraosseous length of each pin was measured. Statistic analyses were performed with the Kruskal-Wallis test, with significance set at P < .05. RESULTS The mean length for the 55° tibial tunnel was 50.3 mm (range, 42 to 56 mm); for the 50° tunnel, it was 48.9 mm (range, 44 to 55 mm); for the 50° anterior tunnel, it was 47.6 mm (range, 39 to 55 mm); and for the 45° tunnel, it was 47.3 mm (range, 41 to 52 mm). Changing the angle of the tibial guide did not significantly affect the length of the tibial tunnel (P = .18). Changing the external tibial starting point did not affect the length of the tibial tunnel (P = .39). CONCLUSIONS Changing the tibial guide angle between 45°, 50°, and 55° does not appreciably change tibial tunnel length. Moving the starting point anterior 1.5 cm toward the tibial tubercle also has no effect on the tibial tunnel length. The lack of significant changes in tunnel length with these interventions may reflect the associated changes that occur in proximal tibial morphometry with change in external tibial starting position. CLINICAL RELEVANCE Changing tibial tunnel length in ACL reconstruction likely requires more distalization of the external tibial starting point than is achieved simply by altering the tibial aiming guide angle by 10° or less.

A Simple Radiographic Sign of Vertical Anterior Cruciate Ligament Tunnel Placement.

The purpose of this study is to describe a novel radiographic sign indicative of vertical tunnel placement following anterior cruciate ligament (ACL) reconstruction. We reviewed 190 consecutive ACL reconstructions. Operative records, patient charts, arthroscopic images, and preoperative and postoperative orthogonal plain radiographic images were reviewed. We made special note of the operative technique. Note was made of tunnel position and whether the posterior (proximal) aspect of Blumensaat line was violated on standard lateral knee radiographic images. Of 190 patients, 17 patients did not have postoperative imaging and were excluded. Of the 173 remaining knees, 163 were primary ACL reconstructions and 10 were revision ACL reconstructions. We found that no anatomically placed ACL femoral tunnel violated Blumensaat line. In all revision cases exhibiting violation of Blumensaat line, a new femoral tunnel was able to be drilled while completely avoiding the previously placed, nonanatomic ACL femoral tunnel. The principal findings of our study demonstrate that violation of Blumensaat line following ACL reconstruction is an indicator of vertical, nonanatomic femoral tunnel placement. Furthermore, presence of this radiographic sign indicates that an anatomically placed femoral tunnel may be drilled while completely avoiding the existing femoral tunnel during cases of revision ACL reconstruction.