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Biomedical subjects

Christopher S Ahmad

Publications and source records attributed to Christopher S Ahmad.

At least 19 recordsLinked to original sources
PubMed2006

Biomechanical evaluation of subscapularis repair used during shoulder arthroplasty.

Dysfunction of the subscapularis after total shoulder replacement has become concerning and may represent poor tendon healing after surgical repair. The objectives of this study were to evaluate the restoration of subscapularis footprint anatomy and failure strength for subscapularis repair via transosseous tunnels and a second anatomic repair via combined transosseous tunnels and direct tendon-to-tendon repair. Six matched pairs of fresh-frozen human cadaveric shoulders were used, with one shoulder from each pair randomly assigned to a transosseous repair and the contralateral shoulder assigned to a combined transosseous tunnel and direct tendon-to-tendon repair. The repair footprint was digitized. Cyclic loading to the tendon repair was performed followed by a constant ramp displacement to complete failure. The transosseous tunnel repair insertional footprint area (228.6 mm2) was significantly less than that of the native footprint (697.3 mm2), and the footprint centroid moved 9.1 mm medially (P = .0001) and 5.5 mm superiorly (P = .003). The combined repair required a statistically significantly greater number of cycles (P = .028) to reach a 5-mm gap (205.7 +/- 65.1) than did the isolated transosseous tunnel technique (76.4 +/- 34.2). A similar greater number of cycles was observed for the 10-mm gap (P = .01) for combined repair (307.5 +/- 82.4) compared with isolated transosseous repair (166.2 +/- 85.8). This study has shown that transosseous tunnel repair alters subscapularis insertional anatomy, resulting in weaker strength of fixation and less contact area when compared with combined transosseous tunnel and direct tendon-to-tendon repair.

Aged↗
PubMed2006

Shoulder adaptive changes in youth baseball players.

Shoulder adaptive changes in response to overhand throwing have been observed in adults, but the age of onset and progression of these adaptive changes have not been established. Two-hundred ninety-eight youth baseball players (8- to 28-year-olds) were studied to determine whether shoulder range of motion and laxity differences between the dominant and non-dominant shoulders exist between different age groups. The subjects were separated into 3 different age groups of 100 8- to 12-year-olds (Group 1), 100 13- to-14 year-olds (Group 2), and 98 15- to 28-year-olds (Group 3). For dominant shoulder external rotation with the humerus in abduction, all groups were significantly different from each other, with Group 2 having the greatest range and Group 1 having the smallest range (P < .05). When comparing dominant shoulder internal rotation in abduction among different groups, Group 3 and Group 2 motion was significantly less than that for Group 1 (P < .05.) When comparing dominant to non-dominant shoulder motion within each group, a significant increase in dominant shoulder external rotation in abduction was found in all 3 age groups (P < .05). Comparison of the differences in external rotation in abduction between the dominant and non-dominant shoulders demonstrated an increase with increasing age, Group 1 (1.5 +/- 6.8 degrees), Group 2 (9.6 +/- 15.3 degrees), and Group 3 (15.0 +/- 11.2 degrees; P < .05). Comparison of differences in internal rotation in abduction between dominant and non-dominant shoulders demonstrated a decrease with increasing age, Group 1 (4.6 +/- 8.2 degrees), Group 2 (8.4 +/- 14.5 degrees), and Group 3 (15.5 +/- 11.7 degrees; P < .05). For shoulder laxity, Groups 2 and 3 had significantly more inferior shoulder laxity when compared to Group 1. In summary, our results indicate that shoulder range of motion and laxity of youth baseball players are caused by adaptive changes that manifest during adolescence.

Adaptation, Physiological↗
PubMed2006

Arthroscopic distal clavicle resection: a comparison of bursal and direct approaches.

PURPOSE: To test the hypothesis that the direct (superior) approach to arthroscopic distal clavicle resection is as safe and effective as the bursal (subacromial) approach. METHODS: All patients who had an arthroscopic distal clavicle resection in our institution between 1994 and 2002 were reviewed. Patients with a history of acromioclavicular joint (ACJ) instability, previous shoulder surgery, glenohumeral pathology, full-thickness rotator cuff tear, or other significant orthopaedic comorbidity were excluded. Outcome data were collected including the American Shoulder and Elbow Surgeons (ASES) score as well as subjective ratings of pain and instability. RESULTS: Follow-up was completed on 66 shoulders of 60 patients. Twenty-four shoulders had a bursal approach (group I) and 42 had a direct approach (group II). There were 45 men and 15 women with an average age of 46 years (range, 21 to 78 years). Follow-up averaged 6.0 years (range, 2 to 11.5 years). The average ASES score was 90 (range, 53-100) in group I and 94 (range, 55-100) in group II. Four patients (10%) in group II required reoperation: 2 patients required ACJ stabilization at 6 and 9 months postoperatively because of anteroposterior instability, and 2 patients required resection again at 5 years because of recurrent symptoms. CONCLUSIONS: Both the direct and bursal approaches lead to satisfactory outcomes in the majority of patients with ACJ arthrosis. However, the direct approach to the ACJ may damage the superior capsular ligaments, potentially leading to distal clavicle instability. Care should be taken when performing the direct ACJ resection to avoid disrupting the capsular restraints. LEVEL OF EVIDENCE: Level IV therapeutic case series.

Adult↗
PubMed2006

"Transosseous-equivalent" rotator cuff repair technique.

In order to optimize healing biology at a repaired rotator cuff footprint, we have developed a "transosseous-equivalent" rotator cuff repair that can be performed arthroscopically. What the arthroscopically repaired tendon experiences is "equivalent" to what is experienced with a traditional open suture-bridge technique. This repair maximizes the utility of a single-row repair technique by preserving the suture limbs of the medial single-row and bridging these sutures over the footprint insertion with distal-lateral interference screw suture fixation; the medial row uses a mattress suture configuration. The geometry of the construct compresses the tendon, optimizing tendon-to-tuberosity contact dimensions, while providing strength sufficient to withstand immediate postoperative rehabilitation.

Arthroscopy↗
PubMed2006

The management of acromioclavicular joint osteoarthrosis: débride, resect, or leave it alone.

The acromioclavicular joint is a small, diarthrodial joint that can cause significant pain. A thorough patient history, careful physical examination, and the judicious use of selective injections are critically important to making an accurate diagnosis. Many radiographic findings are unreliable in determining the reasons for a symptomatic acromioclavicular joint. Recent controversy surrounding this joint has centered on the clinical question: should the acromioclavicular joint be left alone, débrided, or resected? A review of the anatomy, pathophysiology, biomechanics, diagnostic criteria, and treatment options for patients with disorders of the acromioclavicular joint can provide information to answer this question.

Acromioclavicular Joint↗
PubMed2005

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-to-hamstring 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.

Adolescent↗
PubMed2005

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 tendon's 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 degrees of internal rotation and 60 degrees 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.

Arthroscopy↗
PubMed2005

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 x 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 mm(2)) compared with the suture anchor simple (34.1 +/- 9.4 mm(2)) and suture anchor mattress (26.0 +/- 5.3 mm(2)) 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.

Animals↗
PubMed2005

Ulnar collateral ligament of the elbow.

Recent advances in the diagnosis and treatment of the overhead athlete's elbow has led the medical community to understand that the ulnar collateral ligament (UCL) of the elbow is more commonly injured than originally thought. Injury can result in secondary symptoms and problems in other regions of the elbow. Sports requiring an overhead motion, such as throwing a ball, hitting a ball overhead, or serving a tennis ball, imparts a valgus stress on the elbow that is resisted by the UCL. Throwing sidearm or hitting a forehand in tennis, squash, or racquetball may also impart a valgus stress to the elbow. Repeated or excessive valgus stress places a force on the UCL that may result in injury to the ligament. Injury to the UCL may result in problems in other areas of the elbow, including the ulnar nerve, the flexor-pronator musculotendinous unit, the radiocapitellar joint and the posterior compartment of the elbow, in addition to being a cause of loose bodies within the elbow. This article reviews the anatomy, biomechanics, and pathophysiology of injury to the UCL and injuries to the other structures that result from UCL injury. Also reviewed are patient history, examination techniques, tests that help confirm the diagnosis of UCL injury, and treatment of the injured UCL.

Arthroscopy↗
PubMed2005

A survey of sports medicine specialists investigating the preferred management of contaminated anterior cruciate ligament grafts.

PURPOSE: To survey leaders in sports medicine who perform anterior cruciate ligament (ACL) reconstructions to determine the preferred management when ACL graft contamination occurs. TYPE OF STUDY: Survey study of expert opinions and experiences on the management of ACL graft contamination. METHODS: We mailed 337 surveys to directors of academic sports medicine programs and graduates from an accredited sports medicine fellowship. The survey questioned the incidence, treatment, and outcome of ACL graft contamination. RESULTS: Twelve surveys were returned to sender; 196 surgeons responded from the remaining 325 surveys (60%). Forty-nine of 196 (25%) surgeons reported at least 1 contamination during their career. Of those 49, 43 surgeons (88%) had 1 contaminated graft, 5 (10%) had 2, and 1 had 4, for a total of 57 reported contaminated grafts. Of the surgeons who reported a contaminated graft, 22 (45%) performed between 40 and 100 ACL reconstructions annually, and 17 (35%) performed more than 100 ACL reconstructions annually. Forty-three of the 57 (75%) contaminated grafts were managed with cleansing of the graft and proceeding with reconstruction. Ten (18%) were managed by harvesting a different graft, and 4 (7%) were substituted with an allograft. No infections in any of the contaminated grafts were reported. Sixty-five of the 147 (43%) surgeons without graft contamination gave hypothetical management responses. Thirty-eight (58%) would cleanse the graft and proceed with the procedure, 22 (34%) would harvest a different graft, and 5 (8%) would use an allograft. CONCLUSIONS: Surgeons who perform a high volume of ACL reconstruction surgery most often choose graft cleansing as the preferred management for intraoperative ACL graft contamination. LEVEL OF EVIDENCE: Level V, expert opinion.

Anterior Cruciate Ligament↗
PubMed2004

Valgus extension overload syndrome and stress injury of the olecranon.

Basic science studies have improved our understanding of the pathomechanics for valgus extension overload and olecranon stress fractures. These disorders result from repetitive abutment of the olecranon into the olecranon fossa combined with valgus torques, resulting in impaction and shear along the posteromedial olecranon. The patient history and physical examination are similar for each disorder. Imaging studies including plain radiographs, computed tomography, MRI or bone scan may be necessary for accurate diagnosis. Clinical and basic science support mandatory and careful assessment of the medial collateral ligament when valgus extension overload is identified and limited debridement of the olecranon when surgery is indicated. For stress fractures that fail nonoperative management, treatment with internal fixation provides good results.

Athletic Injuries↗
PubMed2004

Elbow anatomy and structural biomechanics.

The elbow is a trochoginglymus joint with three articulations (the ulnohumeral, radiocapitellar, and proximal radioulnar joints) and two degrees of freedom (flexion/extension and pronation/supination). The congruity of the articulations as well as the medial and lateral collateral ligament complexes account for a majority of the stability of the joint. Muscles play a dynamic role in stabilizing the elbow. Understanding the anatomy and biomechanics of the elbow is essential to diagnosing and treating problems that develop in a patient's elbow.

Biomechanical Phenomena↗
PubMed2004

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.

Adult↗
PubMed2004

Medial collateral ligament strain with partial posteromedial olecranon resection. A biomechanical study.

BACKGROUND: Partial resection of the posteromedial aspect of the olecranon in the treatment of valgus extension impingement osteophytosis is a well-described technique. It has been hypothesized that removal of the normal olecranon process, beyond the osteophytic margin, increases the strain in the anterior bundle of the medial collateral ligament. METHODS: We used an electromagnetic tracking device to investigate the strain in the anterior bundle of the medial collateral ligament as a function of increasing applied torque and posteromedial resections of the olecranon in seven cadaveric elbows. Applied torques under valgus stress consisted of hand weight, hand weight plus 1.75 Nm, and hand weight plus 3.5 Nm. Resections were conducted in sequential 3-mm increments, from 0 to 9 mm. We measured changes in the length of the anterior and posterior bands of the anterior bundle of the medial collateral ligament with strain gauges. The strains of the two bands were averaged, and the average was reported. RESULTS: The strain in the anterior bundle of the medial collateral ligament was found to increase with increasing flexion angle, valgus torque, and olecranon resection beyond 3 mm. In two elbows, the anterior bundle of the medial collateral ligament ruptured during testing following the 9-mm resection. There was a significant difference between the strain following the 6-mm resection and that following the 3-mm resection at 110 degrees of flexion with 3.5 Nm of added torque (p = 0.004). CONCLUSIONS: In this in vitro cadaver study, an increase in flexion angle, an increase in valgus torque, and resection of > or =6 mm led to an increase in strain in the anterior bundle of the medial collateral ligament. The non-uniform change in strain related to 3 mm of resection suggests that resections of the posteromedial aspect of the olecranon of >3 mm may jeopardize the function of the anterior bundle.

Aged↗
PubMed2004

Thermal capsulorrhaphy.

The initial wave of enthusiasm for thermal capsulorrhaphy has subsided. Long-term clinical data were lacking until D'Alessandro et al's prospective study indicated the results were not as promising as the previously reported short-term studies. Complications including obliteration or attenuation of capsular tissue, axillary nerve injury, and chondrolysis have all been reported in recent years further raising concern about the widespread use of this procedure. The inexact nature of how much "shrinkage" is being performed has led surgeons to further develop surgical technique in capsular plication, shift, or advancement. Although it remains to be seen if these techniques will lead to good clinical outcomes, it appears that they more closely resemble the original operative procedure-anterior capsular shift.

Axilla↗
PubMed2003

Arthroscopic biceps tenodesis.

The proximal biceps tendon is a significant source of shoulder pain that may be treated with biceps tenotomy or tenodesis. Biceps tenodesis has suggested advantages over tenotomy that include maintenance of the length-tension relationship, prevention of muscle atrophy, maintenance of elbow flexion and supination strength, avoidance of cramping pain, and avoidance of cosmetic deformity. The recent advancement of all arthroscopic tenodesis techniques has provided sufficient fixation strength while easing technical demands and minimizing neurovascular injury risk. With our newer techniques and better understanding of proximal biceps tendon pathology, the indications for tenodesis are evolving, and longer-term follow-up is required to fully evaluate the outcome of these procedures.

Adolescent↗