Christopher S. Ahmad

Immediate Surgical Repair of the Medial Patellar Stabilizers for Acute Patellar Dislocation: A Review of Eight Cases

An open surgical repair of the injured medial patellar stabilizers, including the vastus medialis obliquus muscle and the medial patellofemoral ligament, after acute patellar dislocation was studied in eight patients. At initial examination, all patients had tenderness over the adductor tubercle and a positive patellar apprehension sign. Four of eight patients had obvious ecchymosis over the adductor tubercle. Magnetic resonance imaging, diagnostic arthroscopy, and open surgical exploration documented injury to both the medial patellofemoral ligament and the origin of the vastus medialis obliquus muscle. In all patients, the torn muscle was retracted in an anterior and superior direction and an arthroscopic lateral release was performed followed by open primary repair of the medial patellofemoral ligament to the adductor tubercle and repair of the vastus medialis obliquus muscle to the adductor magnus tendon. Patients were evaluated postoperatively with the Kujala scoring questionnaire. The average follow-up was 3.0 years, with a minimum of 1.5 years. No patients experienced a recurrent dislocation. The average Kujala score was 91.9. Patients rated their return to athletic activity at an average 86% of their pre-injury level. The average subjective satisfaction was 96%. In appropriate cases of acute patellar dislocation, we recommend primary repair of the medial patellofemoral ligament and the vastus medialis obliquus muscle to avoid recurrent dislocation, chronic subluxation, pain, and disability.

Mechanical Properties of Soft Tissue Femoral Fixation Devices for Anterior Cruciate Ligament Reconstruction

Purpose To evaluate femoral soft tissue fixation for anterior cruciate ligament reconstruction. Hypothesis Femoral fixation devices have different ultimate strengths and slippage under cyclic loading. Study Design Controlled laboratory study. Methods Thirty-three porcine femora were used to study interference screw (9), Endobutton (8), Rigidfix cross-pin (8), and Bio-Transfix cross-pin (8) fixation methods. Fixation slippage was evaluated under cyclical load from 50 N to 250 N using a materials testing machine. Ultimate load was determined with a single load to failure. Results Total graft slippage was greater (P< .001) for the Rigidfix (6.02 ± 2.12 mm) and the interference screw (5.44 ± 3.25 mm) compared to the Endobutton (1.75 ± 0.97 mm) and the Bio-Transfix (1.14 ± 0.53 mm). All techniques showed the greatest slippage during the first 100 cycles (Rigidfix 84%, Endobutton 70%, interference screw 56%, and Bio-Transfix 55%). The failure load for the interference screw technique (539 ± 114 N) was lower (P= .0008) than for the other 3 techniques (737 ± 140 N for Rigidfix, 746 ± 119 N for Bio-Transfix, and 864 ± 164 N for Endobutton). Conclusions The interference screw and the Rigidfix fixation demonstrated inferior fixation biomechanics compared to the Bio-Transfix and the Endobutton techniques.

Tendon-to-Bone Pressure Distributions at a Repaired Rotator Cuff Footprint Using Transosseous Suture and Suture Anchor Fixation Techniques

Background Interface contact pressure between the tendon and bone has been shown to influence healing. This study evaluates the interface pressure of the rotator cuff tendon to the greater tuberosity for different rotator cuff repair techniques. Hypothesis The transosseous tunnel rotator cuff repair technique provides larger pressure distributions over a defined insertion footprint than do suture anchor techniques. Study Design Controlled laboratory study. Methods Simulated rotator cuff tears over a 1 × 2-cm infraspinatus insertion footprint were created in 25 bovine shoulders. A transosseous tunnel simple suture technique (n = 8), suture anchor simple technique (n = 9), and suture anchor mattress technique (n = 8) were used for repair. Pressurized contact areas and mean pressures of the repaired tendon against the tuberosity were determined using pressure-sensitive film placed between the tendon and the tuberosity. Results The mean contact area between the tendon and tuberosity insertion footprint was significantly greater for the transosseous technique (67.7 ± 5.8 mm2) compared with the suture anchor simple (34.1 ± 9.4 mm2) and suture anchor mattress (26.0 ±5.3 mm2) techniques (P < .05). The mean interface pressure exerted over the footprint by the tendon was also greater for the transosseous technique (0.32 ± 0.05 MPa) compared with the suture anchor simple (0.26 ± 0.04 MPa) and suture anchor mattress (0.24 ± 0.02 MPa) techniques (P < .05). Conclusion The transosseous tunnel rotator cuff repair technique creates significantly more contact and greater overall pressure distribution over a defined footprint when compared with suture anchor techniques. Clinical Relevance Stronger and faster rotator cuff healing may be expected when beneficial pressure distributions exist between the repaired rotator cuff and its insertion footprint. Tendon-to-tuberosity pressure and contact characteristics should be considered in the development of improved open and arthroscopic rotator cuff repair techniques.

Biomechanical Evaluation of a New Ulnar Collateral Ligament Reconstruction Technique with Interference Screw Fixation

Background Techniques for ulnar collateral ligament reconstruction have evolved. Hypothesis Ulnar collateral ligament reconstruction with interference screw fixation restores elbow kinematics and failure strength to that of the native ligament. Study Design Controlled laboratory study. Methods Of 10 matched pairs of cadaveric elbows, one underwent kinematic testing under conditions of an intact, released, and reconstructed ligament. Single 5-mm diameter bone tunnels were created at the isometric anatomic insertion sites on the medial epicondyle and sublime tubercle. Graft fixation was achieved with 5 × 15 mm soft tissue interference screws. The reconstructed and contralateral intact elbows were then tested to failure. Results Average stiffness for intact elbows (42.81 ± 11.6 N/mm) was significantly greater than for reconstructed elbows (20.28 ± 12.5 N/mm). Ultimate moment for intact elbows (34.0 ± 6.9 N·m) was not significantly different from reconstructed elbows (30.6 ± 19.2 N·m). Release of the ulnar collateral ligament caused a significant increase in valgus instability. Reconstruction restored valgus stability to near that of the intact elbow. Conclusions With this reconstruction method, failure strength was comparable with that of the native ligament and physiologic elbow kinematics were reliably restored. Clinical Relevance This technique returns elbow kinematics to near normal, with less soft tissue dissection and risk of ulnar nerve injury and ease of graft insertion, tensioning, and fixation.

Dynamic Contributions of the Flexor-pronator Mass to Elbow Valgus Stability

BACKGROUND Previous studies have indicated that the demands placed on the medial ulnar collateral ligament of the elbow when it is subjected to valgus torque during throwing exceed its failure strength, which suggests the necessary dynamic contribution of muscle forces. We hypothesized that the flexor-pronator mass assists the medial ulnar collateral ligament in stabilizing the elbow against valgus torque. METHODS Six cadaveric elbows were tested at 30 degrees and 90 degrees of flexion with no other constraints to motion. A full medial ulnar collateral ligament tear was simulated in each elbow. Muscle forces were simulated on the basis of the centroids and physiological cross-sectional areas of individual muscles. The biceps, brachialis, and triceps were simulated during flexor carpi ulnaris, flexor digitorum superficialis, flexor digitorum superficialis and flexor carpi ulnaris, and pronator teres-loading conditions. Kinematic data were obtained at each flexion angle with use of a three-dimensional digitizer. RESULTS Release of the medial ulnar collateral ligament caused a significant increase in valgus instability of 5.9 degrees +/- 2.4 degrees at 30 degrees of elbow flexion and of 4.8 degrees +/- 2.0 degrees at 90 degrees of elbow flexion (p < 0.05). The differences in valgus angulation between each muscle-simulation condition and the medial ulnar collateral ligament-intact condition were significantly different from each other (p < 0.05), except for the difference between the flexor carpi ulnaris contraction condition and the flexor digitorum superficialis-flexor carpi ulnaris co-contraction condition. This co-contraction provided the most correction of the valgus angle in comparison with the intact condition at both 30 degrees and 90 degrees of elbow flexion (1.1 degrees +/- 1.8 degrees and 0.38 degrees +/- 2.3 degrees , respectively). Simulation of the flexor carpi ulnaris alone provided the greatest reduction of the valgus angle among all individual flexor-pronator mass muscles tested (p < 0.05), whereas simulation of the pronator teres alone provided the least reduction of the valgus angle (p < 0.05). CONCLUSIONS The flexor-pronator mass dynamically stabilizes the elbow against valgus torque. The flexor carpi ulnaris is the primary stabilizer, and the flexor digitorum superficialis is a secondary stabilizer. The pronator teres provides the least dynamic stability.

Tendon-Bone Interface Motion in Transosseous Suture and Suture Anchor Rotator Cuff Repair Techniques

Background Although many studies involving rotator cuff repair fixation have focused on ultimate fixation strength and ability to restore the tendons native footprint, no studies have characterized the stability of the repair with regard to motion between the tendon and repair site footprint. Hypothesis Suture anchor fixation for rotator cuff repair has greater interface motion between tendon and bone than does transosseous suture fixation. Study Design Controlled laboratory study. Methods Twelve fresh-frozen human cadaveric shoulders were tested in a custom device to position the shoulder in internal and external rotations with simulated supraspinatus muscle loading. Tendon motion relative to the insertional footprint on the greater tuberosity was determined optically using a digital camera rigidly connected to the humerus, with the humerus positioned at 60° of internal rotation and 60° of external rotation. Testing was performed for the intact tendon, a complete supraspinatus tear, a suture anchor repair, and a transosseous tunnel repair. Results Difference in tendon-bone interface motion when compared with the intact tendon was 7.14 ± 3.72 mm for the torn rotator cuff condition, 2.35 ± 1.26 mm for the suture anchor repair, and 0.02 ± 1.18 mm for the transosseous suture repair. The transosseous suture repair demonstrated significantly less motion when compared with the torn rotator cuff and suture anchor repair conditions (P <. 05). Conclusion Transosseous suture repair compared with suture anchor repair demonstrated superior tendon fixation with reduced motion at the tendon-to-tuberosity interface. Clinical Relevance Development of new fixation techniques for arthroscopic and open rotator cuff repairs should attempt to minimize interface motion of the tendon relative to the tuberosity.

Clinical Outcomes of the DANE TJ Technique to Treat Ulnar Collateral Ligament Insufficiency of the Elbow

Background Many improvements in ulnar collateral ligament reconstruction have been made since Jobe et al first described the procedure. A novel elbow ulnar collateral ligament reconstruction technique that combines interference screw fixation on the ulna with docking of the graft on the humeral side (DANE TJ) has been reported. Hypothesis Outcomes of ulnar collateral ligament reconstructions performed with the DANE TJ technique are as good as other recently published results of ulnar collateral ligament reconstruction, particularly in cases of insufficient bone stock on the sublime tubercle and revision reconstructions. Study Design Case series; Level of evidence, 4. Methods During a 3-year period, 22 athletes were treated with surgical reconstruction of the ulnar collateral ligament using proximal docking and distal interference screw fixation of the ligament (DANE TJ technique). All patients had a history, physical examination findings, and magnetic resonance imaging results consistent with ulnar collateral ligament injury. Patients were evaluated at a mean of 36 months postoperatively. Outcomes were classified using a modified Conway Scale. Results At the most recent follow-up, 19 of 22 patients had excellent results. There were 2 fair results and 1 poor result. The poor result was in a revision case. The 2 other revision ulnar collateral ligament reconstructions had excellent outcomes. When used in 2 cases of sublime tubercle avulsions, the results were excellent. Postoperative complications occurred in 4 patients: 2 developed ulnar neuritis, and 2 required second surgeries for lysis of adhesions. Three of these 4 patients went on to have excellent outcomes. Conclusion Clinically, the initial results compare favorably with other published techniques of elbow ulnar collateral ligament reconstruction. These early data support the use of the DANE TJ technique for revision cases and cases of sublime tubercle insufficiency.

The Docking Technique for Medial Patellofemoral Ligament Reconstruction: Surgical Technique and Clinical Outcome

Background Current techniques of medial patellofemoral ligament (MPFL) reconstruction vary with respect to methods of fixation on the femur and the patella. This article presents the outcomes of a surgical technique for reconstruction of the MPFL that uses a soft tissue graft with interference screw fixation on the femur and a docking technique for fixation on the patella. Hypothesis Patients with patellar instability who are treated with the docking technique for MPFL reconstruction will have improvements in knee symptoms and function, with a high percentage achieving good to excellent results at early follow-up. Study Design Case series; Level of evidence, 4. Methods Twenty consecutive patients with patellar instability underwent reconstruction of the MPFL. Patients were evaluated preoperatively and postoperatively by physical and radiographic examination and subjectively with the IKDC (International Knee Documentation Committee), Tegner, Kujala, and Lysholm questionnaires. Nineteen patients underwent magnetic resonance imaging preoperatively. Results The average follow-up was 31 months (range, 24–39). No recurrent episodes of dislocation or subluxation were reported. A firm endpoint to lateral patellar translation was noted in all patients at most recent follow-up. The IKDC subjective knee evaluation score improved from 42 preoperatively to 82 postoperatively (P < .001); Kujala, from 50 to 88 (P < .001); Lysholm, from 50 to 89 (P < .001); and Tegner, from 3.6 to 5.6 (P < .001). Conclusion The docking technique for MPFL reconstruction is an effective surgical procedure for the treatment of patellar instability.

Effect of Gender and Maturity on Quadriceps-to-Hamstring Strength Ratio and Anterior Cruciate Ligament Laxity:

Background Exercise programs have been introduced to reduce the ACL injury risk in female athletes. The most effective age at which to start these programs is not known. Hypothesis Age and gender affect ligament laxity and quadriceps-to-hamstring strength ratio. Study Design Cross-sectional study; Level of evidence, 3. Methods Fifty-three female and 70 male recreational soccer players, 10 to 18 years of age, were studied with physical examination, KT-1000 arthrometry, and manual maximum quadriceps and hamstring strength using a handheld dynamometer. The subjects were separated into 4 groups to examine maturity-related intergender differences: group G1, premenarchal girls (n = 24); group B1, boys 13 years and younger (n = 38); group G2, girls 2 or more years after menarche (n = 29); and group B2, boys 14 years and older (n = 32). Results Both knees of 123 soccer players were evaluated. The mean ages for groups G1, B1, G2, and B2 were 11.50 ± 1.69, 10.63 ± 1.85, 15.5 ± 1.43, and 15.59 ± 1.24 years, respectively, and the mean laxity measurements were 8.84 ± 2.12, 8.51 ± 1.61, 8.85 ± 1.86, and 7.33 ± 1.27 mm, respectively. Laxity was significantly less for the mature boys (P= .0015) than for the immature boys, mature girls, and immature girls. With increasing maturity, significant increases in both quadriceps and hamstring muscle strength were observed for both boys and girls (P< .05). Boys demonstrated a greater percentage increase in hamstring strength with maturity (179%) compared with girls (27%) (P< .05). Mature girls (2.06) had significantly greater quadriceps-tohamstring ratio when compared with immature girls (1.74), immature boys (1.58), and mature boys (1.48) (P< .05). Conclusion Female athletes after menarche increase their quadriceps strength greater than their hamstring strength, putting them at risk for anterior cruciate ligament injury. Anterior cruciate ligament–prevention programs based on improving dynamic control of the knee by emphasizing hamstring strengthening should be instituted for girls after menarche.

Simulation of surgical glenoid resurfacing using three-dimensional computed tomography of the arthritic glenohumeral joint: The amount of glenoid retroversion that can be corrected

HYPOTHESIS The magnitude of glenoid retroversion that can be surgically corrected in total shoulder arthroplasty and still enable implantation of a glenoid component has not been established. We hypothesized that increased retroversion will require smaller glenoid components for successful implantation when the glenoid is surgically corrected and that correction beyond 20 degrees of retroversion is not feasible without peg penetration. METHODS Using 3-dimensional models created from computed tomography of 19 patients with advanced shoulder osteoarthritis, we simulated glenoid resurfacing on varying degrees of retroverted, osteoarthritic glenoids using an in-line 3-peg glenoid component and asymmetric reaming to correct version. RESULTS Glenoids with preoperative retroversion of less than 12 degrees could always be implanted with 46-mm and 52-mm glenoid components at neutral version without vault violation. Conversely, glenoids with greater than 18 degrees of preoperative retroversion could not be implanted at neutral version due to vault violation from the pegs. The average preoperative glenoid retroversion of patients in which a 46-mm glenoid was implanted at neutral version was 8.9 degrees +/- 6.4 degrees compared with 19.0 degrees +/- 7.1 degrees for those that could not be implanted at neutral (P = .005). DISCUSSION Computer-aided surgical simulation shows that glenoid retroversion is a critical factor in determining successful glenoid implantation. Smaller sized glenoid components allow for greater version correction and less residual postsimulation retroversion when an in-line pegged component is used.