Michael F. Dillingham

Biomechanical considerations in patellofemoral joint rehabilitation

Patellofemoral joint biomechanics during leg press and leg extension exercises were compared in 20 normal subjects (10 men, 10 women) aged 18 to 45 years. Knee moment, patellofemoral joint reaction force, and patellofemoral joint stress were calculated for each subject at four knee flexion angles (0°, 30°, 60°, and 90°) during leg press and leg extension exercises. All three parameters (knee moment, patellofemoral joint reaction force, and patellofemoral joint stress) were significantly greater in leg extension exercise than leg press exercise at 0° and 30° of knee flexion (P < 0.001). At 60° and 90° of knee flexion, all three param eters were significantly greater in leg press exercise than leg extension exercise (P < 0.001). Patellofemoral joint stresses for leg press and leg extension exercises intersected at 48° of knee flexion. This study demonstrates that patients with patello femoral joint arthritis may tolerate rehabilitation with leg press exercise better than with leg extension exercise in functional ranges of motion because of lower patel lofemoral joint stresses.

Normal cervical spine morphometry and cervical spinal stenosis in asymptomatic professional football players. Plain film radiography, multiplanar computed tomography, and magnetic resonance imaging.

Diagnosis of cervical spinal stenosis or instability rests on the objective findings depicted on static and dynamic radiographs. Before abnormal spinal morphometry can be determined, it is first necessary to establish normal values for the specific patient population being evaluated. Several studies have attempted to establish norms for plain film measurements of the cervical spine in children and adults, but few have applied consistent methods for generating precise measurements. The first part of this study established normal values for cervical spinal morphometry and segmental spinal motion in the elite athlete. The second part of this study determined the most accurate screening method for detecting cervical spinal stenosis. Three sagittal diameters of the cervical spinal canal were compared to determine which represented the smallest midline diameter on static and dynamic radiographs. The Torg ratio was also evaluated as a method to detect significant cervical spinal stenosis and was shown to have a high sensitivity but poor positive predictive value. The study clarified why the ratio yields a large number of false positive cases. From the results of this study, an algorithm has been developed for the evaluation of stenosis of the cervical spine in athletes.

Magnetic resonance imaging of articular cartilage of the knee: comparison between fat-suppressed three-dimensional SPGR imaging, fat-suppressed FSE imaging, and fat-suppressed three-dimensional DEFT imaging, and correlation with arthroscopy.

To compare signal‐to‐noise ratios (S/N) and contrast‐to‐noise ratios (C/N) in various MR sequences, including fat‐suppressed three‐dimensional spoiled gradient‐echo (SPGR) imaging, fat‐suppressed fast spin echo (FSE) imaging, and fat‐suppressed three‐dimensional driven equilibrium Fourier transform (DEFT) imaging, and to determine the diagnostic accuracy of these imaging sequences for detecting cartilage lesions in osteoarthritic knees, as compared with arthroscopy.

Septic arthritis in postoperative anterior cruciate ligament reconstruction.

A review of postoperative infected anterior cruciate ligament reconstructions was done on 3500 consecutive arthroscopic procedures. The purpose was to assess incidence, diagnosis, treatment, and outcome factors. Six postoperative intraarticular infections were detected. Average followup was 3 years (range, 2–8 years). The rate of infection was 0.14%. Five men and one woman with a median age of 32.5 years (range, 20–51 years) comprised the study group. The average interval from the onset of symptoms to the initial arthroscopic intervention was 7.5 days (range, 2–20 days). Staphylococcus aureus was present in three knees, Staphylococcus epidermidis in two, and Streptococcus nonhemolytic in one. All patients had initial arthroscopic debridement and lavage followed by 6 weeks of intravenous antibiotics. Two grafts were removed: one patient had delayed ligament reconstruction and the other had total knee arthroplasty. The remaining patients had full range of motion. In the group with the best result, two patients had Staphylococcus epidermidis and one had Staphylococcus aureus, which was treated 2 days after clinical symptoms began. The other two patients infected with Staphylococcus aureus had unsatisfactory results. Anterior cruciate ligament infection is rare, but diagnosable. When treated early with appropriate antibiotic therapy and arthroscopic debridement, four of six grafts were retained. If the infection does not respond rapidly to early therapy, then graft removal is an option.

Turf-toe: An analysis of metatarsophalangeal joint sprains in professional football players

Metatarsophalangeal joint injuries of the great toe (turf- toe) are receiving increasing attention in the literature because of the prevalence of synthetic surfaces and lighter, more flexible shoes. Eighty active professional football players were evaluated. The mechanism of injury was hyperextension in 85% of the players. Eighty-three percent reported their initial injury on arti ficial turf (P < 0.05). Other factors significantly related to the incidence of turf-toe included player age (P < 0.01), number of years in professional football (P < 0.01), and range of ankle dorsiflexion (P < 0.05). Turf- toe injury resulted in significantly decreased range of motion of the first metatarsophalangeal joint (P < 0.01).

Histologic evaluation of the glenohumeral joint capsule after the laser-assisted capsular shift procedure for glenohumeral instability.

Glenohumeral joint capsule obtained from 42 patients who had undergone an arthroscopic laser-assisted capsular shift procedure was evaluated histologically. A total of 53 samples from the anterior inferior glenohumeral ligament of the joint capsule were collected before and at various times after the procedure (range, 0 to 38 months). Despite glenohumeral instability, joint capsule of the patients before the procedure showed no significant histologic lesions. Laser treatment significantly altered the histologic properties of the tissue as evidenced by hyalinization of collagen and necrotic cells (time 0). Tissues sampled during the short-term period (3 to 6 months) after the procedure demonstrated fibrous connective tissue with reactive cells and vasculature. Collagen and cell morphology returned to normal in the middle- to long-term period (7 to 38 months) after the procedure, while the number of fibroblasts remained elevated. Joint capsule collected from the shoulders of six patients who experienced stiffness after the procedure showed persistent synovial, cellular, and vascular reaction even after 1 year postoperatively, the cause of which is unclear. This study re-

Anterior cruciate ligament reconstruction using cryopreserved allografts.

Primary ACL reconstruction historically has been done using autograft tissues whereas allografts have been limited to revision cases and patients who are older or with lower physical demands because some animal studies suggested a slower biologic incorporation rate. The purpose of the current study was to evaluate the effectiveness of the cryopreserved Achilles tendon allograft in primary ACL reconstruction in a consecutive series of athletes. Fifty consecutive patients with a strenuous or moderate preinjury activity level, as defined by the International Knee Documentation Committee (IKDC), had ACL reconstruction using cryopreserved Achilles tendon allografts secured with bioabsorbable interference screws. Five patients were professional athletes. The average age of the patients was 36 years (range, 17–50 years). A 3- to 5-year followup study was done in all of the patients using the IKDC form. Tunnel widening was measured in the lateral radiographs at the widest level. The overall outcome was normal or nearly normal in 94% of the patients. No failures were reported in this series. Forty-six patients (92%) returned to their same preinjury sport activity level. The average KT-1000 side-to-side difference was 2.3 mm. Average tibial tunnel widening was 2.7 mm (range, 0–6 mm); no significant correlation was observed between increased tunnel size and a fair or poor clinical outcome. This experience shows that favorable results can be obtained with cryopreserved Achilles tendon allografts in athletes in whom avoiding donor site morbidity may be an issue in terms of a prompt return to sport.

HOLMIUM LASER SURGERY

This relatively new form of laser energy, with its powerful and precise ability to ablate the dense tissues of the musculoskeletal system as well as its transmissibility in fiberoptic cables and a fluid medium, makes this an ideal tool for use in orthopedic surgery. Its importance as a new orthopedic modality may well lie in its unique ability to gain access to small articular compartments while providing superior homeostatic control, thereby decreasing postoperative morbidity. While not yet in widespread use, its popularity is rapidly spreading and research into a variety of new applications is growing steadily.

The pseudoradicular syndrome. Lower extremity peripheral nerve entrapment masquerading as lumbar radiculopathy.

Of approximately 4,000 patients with complaints of lower extremity pain who were referred to our center for evaluation of suspected lumbar radiculopathy, 36 were found to have peripheral nerve entrapments as the sole cause of their leg pain. Nine patients had femoral nerve entrapments just proximal to the inguinal ligament. Seven patients had saphenous nerve entrapments about the knee. Twenty patients had peroneal nerve entrapments at or above the popliteal space. Nine patients had tibial nerve entrapments in the popliteal space. The diagnosis was established on the basis of electrophysiologic studies coupled with the results of selective spinal and peripheral nerve blocks. Seven patients with saphenous nerve lesions, 12 patients with peroneal nerve lesions, nine patients with tlbial nerve lesions, and four patients with femoral nerve lesions, for a total of 32 (71%) cases underwent surgical exploration and external neurolysls. Forty-four percent of the cases had a positive nerve root tension sign, and 44% (20/45) had spinal range of motion abnormalities. Back pain complaints were noted in 49% (22/45) of the cases. The pseudoradicular syndrome should be considered in cases of undiagnosed persistent leg pain. Peripheral nerve lesions should be ruled out prior to considering lumbar spine surgery.

Dynamic MR imaging and stress testing in glenohumeral instability: Comparison with normal shoulders and clinical/surgical findings

Our objectives were to test the hypotheses that: 1) during shoulder motion, glenohumeral alignment differs between asymptomatic shoulders and those with symptomatic instability; 2) during magnetic resonance (MR)‐monitored physical exam or stress testing, glenohumeral alignment differs between asymptomatic shoulders and those with instability; and 3) glenohumeral translation during MR stress testing correlates with findings of shoulder instability by clinical exam and exam under anesthesia (EUA). Using an open‐configuration 0.5 T MR imaging (MRI) system, we studied symptomatic shoulders in 11 subjects and compared them to their contralateral asymptomatic shoulders. Each shoulder was studied during abduction/adduction and internal/external rotation to determine the humeral head position on the glenoid. An examiner also performed the MR stress test on each shoulder by applying manual force on the humeral head during imaging. All shoulders were assigned an instability grade from the MR stress test, and this grade was correlated with: 1) clinical exam grade assigned during preoperative assessment by an orthopedic surgeon and 2) intraoperative instability grade by EUA immediately preceding arthroscopy. With dynamic abduction and internal/external rotation, the humeral head remained centered on the glenoid in 9 of 11 shoulders, but in two subjects there were dramatic demonstrations of subluxation. With stress testing, a trend toward more joint laxity was demonstrated in symptomatic than in asymptomatic joints (P = 0.11). MR grading of instability correlated directly with clinical grading in six cases and underestimated the degree of instability relative to clinical exam in the other cases. MR instability grading systematically underestimated instability compared with EUA in 7 of the 10 cases that underwent surgical repair. We concluded that dynamic MR evaluation of glenohumeral alignment did not demonstrate abnormalities in symptomatic shoulders in 8 of 10 patients, whereas 2 patients showed dramatic findings of subluxation. Manual stress testing during dynamic MR examination showed a strong correlation with clinical instability grading. Dynamic shoulder MR examination during stress testing could, with further validation, become a useful adjunct to shoulder instability evaluations. J. Magn. Reson. Imaging 2001;13:748–756.