Medial patellofemoral ligament (MPFL) reconstruction for the treatment of patellofemoral instability.

Patellofemoral instability can be a disabling problem. Numerous techniques are employed for its treatment. Medial patellofemoral ligament (MPFL) reconstruction in combination with other procedures has been explored by many orthopedic surgeons. The purpose of the study was to determine the effectiveness of isolated MPFL reconstruction in treating the symptoms associated with patellofemoral instability, preventing recurrence of patella dislocation, and returning patients to preinjury level of activity. This is a case series study. We conducted a clinical follow-up study on 56 knees (49 patients) after MPFL reconstruction for recurrent patellar instability with a mean follow-up of 4.3 years (range, 1.1-6.8). A single MPFL reconstruction technique was performed in all cases. Patient outcomes were evaluated using: International Knee Documentation Committee (IKDC) subjective knee form, Tegner activity score, functional hop test, and radiographs. Mean age at time of surgery was 24 years old (range, 13-49). Females comprised 75% of the sample. Mean interval from injury to surgery was 7.2 ± 8.6 years (range, 51 days-37 years). At follow-up, there were no recurrent dislocations reported, patella subluxation in 6 (11%) cases, and radiographic degenerative changes were none to mild in all patients. The series mean IKDC scores at follow-up was 76.3 ± 19.2 (range, 30-99), and Tegner activity scores were 5.6 ± 2.5. MPFL reconstruction is an option for treating the symptoms of patellar instability, preventing recurrent dislocation, and returning patients near to their preinjury level of activity. The level of evidence is IV.

Biomechanical effects of joint line elevation in total knee arthroplasty.

BACKGROUND: Inadequate restoration of the knee joint line after total knee arthroplasty may lead to a poor clinical outcome. The purpose of this study was to quantitatively assess the effects of joint line elevation following total knee arthroplasty with increased joint volume on patellofemoral contact kinematics. METHODS: Six cadaveric specimens were tested. Patellofemoral contact area, contact pressure, and kinematics were measured following total knee arthroplasty with an anatomic joint line and after 4 and 8mm of joint line elevation, at knee flexion angles of 0°, 30°, 60°, 90° and 120°. Repeated measures analysis of variance with a Tukey post hoc test with a significance level of 0.05 was used for statistical analyses. FINDINGS: There was a decrease in contact area with joint line elevation at flexion angles of 60°, 90° and 120° (P=0.009-0.04). There was a significant increase in contact pressure only at 30° of knee flexion with 8mm of joint line elevation (P=0.004). Three of the six specimens showed inferior edge loading of the patella component following 8mm of joint line elevation at 120° of knee flexion. The sagittal plane patellofemoral angle increased significantly with joint line elevation except for 0° knee flexion (P=0.0002-0.02). INTERPRETATION: Knee joint line elevation with increased knee volume significantly affects patellofemoral contact area and kinematics and produced inferior edge loading/impingement between the patella and tibial components, this may result in loss of knee range of motion, postoperative pain, and premature component wear.

Biomechanical and anatomical assessment after knee hyperextension injury.

BACKGROUND: Knee hyperextension can be a serious and disabling injury in both the athletic and general patient population. Understanding the pathoanatomy and pathomechanics is critical for accurate surgical soft tissue reconstructions. PURPOSE: To quantify the effects of knee hyperextension injury on knee laxity in a human cadaveric model and to qualitatively assess the anatomical injury pattern through surgical dissection. STUDY DESIGN: Descriptive laboratory study. METHODS: Six fresh-frozen cadaveric knees were rigidly mounted on a custom knee testing system that simulates clinical laxity tests. The knee laxity measurements consisted of anterior-posterior laxity, internal-external rotational laxity, and varus-valgus laxity using a custom testing setup and a Microscribe 3DLX system. The laxity data were collected at both 30 degrees and 90 degrees of knee flexion for the intact specimens and then after 15 degrees and 30 degrees hyperextension injury. After biomechanical assessment, a detailed dissection was performed to document the injured structures in the knee. Repeated-measures analysis of variance with a Tukey post hoc test (P < .05) was used for statistical comparison. RESULTS: The results from this study suggest progressive damage to translational and rotational knee soft-tissue restraints with increasing knee hyperextension. Knee hyperextension to 30 degrees caused the most significant increase in anterior-posterior and rotational laxity. Anatomical dissections showed a general injury pattern to the posterolateral corner, partial femoral anterior cruciate ligament avulsion in 4 of 6 specimens, and no gross posterior cruciate ligament injuries. CONCLUSION: Injuries to the posterolateral corner of the knee can result from isolated knee hyperextension. CLINICAL RELEVANCE: The clinician should be aware of the potential for posterolateral corner injuries with isolated knee hyperextension. This will allow early surgical planning and primary surgical repair.

Reliability of the international knee documentation committee radiographic grading system.

BACKGROUND: The International Knee Documentation Committee (IKDC) forms are commonly used to measure outcomes after anterior cruciate ligament (ACL) reconstruction. The knee examination portion of the IKDC forms includes a radiographic grading system to grade degenerative changes. The interrater and intrarater reliability of this radiographic grading system remain unknown. HYPOTHESIS: We hypothesize that the IKDC radiographic grading system will have acceptable interrater and intrarater reliability. STUDY DESIGN: Case series (diagnosis); Level of evidence, 4. METHODS: Radiographs of 205 ACL-reconstructed knees were obtained at 5-year follow-up. Specifically, weightbearing posteroanterior radiographs of the operative knee in 35 degrees to 45 degrees of flexion and a lateral radiograph in 30 degrees of flexion were used. The radiographs were independently graded by 2 sports medicine fellowship-trained orthopaedic surgeons using the IKDC 2000 standard instructions. One surgeon graded the same radiographs 6 months apart, blinded to patient and prior IKDC grades. The percentage agreement was calculated for each of the 5 knee compartments as defined by the IKDC. Interrater reliability was evaluated using the intraclass correlation coefficient (ICC) 2-way mixed effect model with absolute agreement. The Spearman rank-order correlation coefficient (r(s)) was applied to evaluate intrarater reliability. RESULTS: The interrater agreement between the 2 surgeons was 59% for the medial joint space (ICC = 0.46; 95% confidence interval [CI] = 0.35-0.56), 54% for the lateral joint space (ICC = 0.45; 95% CI = 0.27-0.58), 49% for the patellofemoral joint (ICC = 0.40; 95% CI = 0.26-0.52), 63% for the anterior joint space (ICC = 0.20; 95% CI = 0.05-0.34), and 44% for the posterior joint space (ICC = 0.28; 95% CI = 0.15-0.40). The intrarater agreement was 83% for the medial joint space (r(s) = .77, P < .001), 86% for the lateral joint space (r(s) = .76, P < .001), 81% for the patellofemoral joint (r(s) = .79, P < .001), 91% for the anterior joint space (r(s) = .48, P < .001), and 69% for the posterior joint space (r(s) = .64, P < .001). CONCLUSIONS: While intrarater reliability was acceptable, interrater reliability was poor. These findings suggest that multiple raters may score the same radiographs differently using the IKDC radiographic grading system. The use of a single rater to grade all radiographs when using the IKDC radiographic grading system maximizes reliability.

The effect of ulnar shortening on lunate and triquetrum motion--a cadaveric study.

BACKGROUND: Ulnar shortening osteotomy is a widely used procedure for a number of pathologic conditions. However, there is little biomechanical data on its effect on the surrounding soft tissue structures. Therefore, the objective of this study was to determine the effects of progressive ulnar shortening on the distal radioulnar joint and the proximal carpal bones. METHODS: The kinematics and strain between the ulnar styloid, lunate, and triquetrum were evaluated with varying supination and pronation forces. Six fresh-frozen cadaveric upper extremity specimens were tested after progressive ulnar shortening using a custom jig. Biomechanical measurements including strain and translation were made by evaluating the change in position of the digitizing markers on the carpal bones, radius and ulna. FINDINGS: There were significant changes in marker positions with respect to intact specimens for each amount of shortening at the ulnar styloid (P<0.001), the lunate (P<0.001), and triquetrum (P<0.001). With progressive ulnar shortening, the strain data demonstrated that there was no significant change in lunato-triquetral strain, but demonstrated a significant increase in both ulno-triquetral and ulno-lunato strain (P<0.04). INTERPRETATION: Progressive ulnar shortening increases ulno-triquetral and ulno-lunato strains with an ensuing reduction in motion between the carpal bones.

Anatomy and biomechanics of the elbow joint.

The elbow joint is a complex structure that provides an important function as the mechanical link in the upper extremity between the hand, wrist and the shoulder. The elbow's functions include positioning the hand in space for fine movements, powerful grasping and serving as a fulcrum for the forearm. Loss of elbow function can severely affect activities of daily living. It is important to recognize the unique anatomy of the elbow, including the bony geometry, articulation, and soft tissue structures. The biomechanics of the elbow joint can be divided into kinematics, stabilizing structures in elbow stability, and force transmission through the elbow joint. The passive and active stabilizers provide biomechanical stability in the elbow joint. The passive stabilizers include the bony articular geometry and the soft tissue stabilizers. The active stabilizers are the muscles that provide joint compressive forces and function. Knowledge of both the anatomy and biomechanics is essential for proper treatment of elbow disorders.

Kinematic analysis of the distal radioulnar joint after a simulated progressive ulnar-sided wrist injury.

A kinematic analysis of a progressive, ulnar-sided wrist injury was performed using a cadaver model to study the static and dynamic stabilizers of the distal radioulnar joint with a 3-dimensional motion tracking system. Anatomically based loads were applied to achieve pronation and supination and then the specimens were evaluated after serial transection of the triangular fibrocartilage, the extensor carpi ulnaris sheath, and the ulnocarpal ligaments. Statistically significant increases in translation of the radius relative to the ulna occurred with sectioning of both the triangular fibrocartilage proper and the extensor carpi ulnaris tendon sheath. No significant change in position of the forearm could be appreciated with subsequent sectioning of the ulnocarpal ligaments. Our observations support the idea that the ulnocarpal ligaments do not need to be surgically reconstructed when there are serious injuries to the triangular fibrocartilage complex.