A Clinical Comparison of Linear- and Surface Area-Based Methods of Measuring Glenoid Bone Loss.

BACKGROUND: The purpose of this study was to determine whether linear-based measurement significantly overestimates glenoid bone loss in comparison with surface area-based measurement in patients with recurrent anterior shoulder instability and glenoid bone loss. HYPOTHESIS: Linear-based measurement will significantly overestimate glenoid bone loss in comparison with surface area-based measurement in patients with anterior shoulder instability and glenoid bone loss. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 3. METHODS: Thirty patients with anterior shoulder instability underwent preoperative bilateral shoulder computed tomography (CT) scans. Three-dimensional CT (3D-CT) reconstruction with humeral head subtraction was performed to obtain an en face view of the 3D-CT glenoid. Glenoid bone loss was measured with the surface area and linear methods of measurement. Statistical analysis was performed with a paired 2-tailed t test. RESULTS: Twenty-eight patients (5 female and 23 male; mean age, 25.1 years; age range, 15-58 years) were included in the study; 17 patients underwent a glenoid augmentation procedure, and 11 underwent arthroscopic Bankart repair. The mean percentage glenoid bone loss calculated with the surface area and linear methods was 12.8% ± 8.0% and 17.5% ± 9.7% ( P < .0001), respectively. For the 17 patients who underwent glenoid augmentation, mean percentage bone loss with the surface area and linear methods was 16.6% ± 7.9% and 23.0% ± 8.0% ( P < .0001), respectively. CONCLUSION: Linear measurement of glenoid bone loss significantly overestimates bone loss compared with surface area measurement in patients with anterior glenoid bony defects. These results indicate that these different methods cannot be used interchangeably and cannot be used with the same critical thresholds for glenoid bone loss.

The Effect of Capsulectomy on Hip Joint Biomechanics.

BACKGROUND: Capsulectomy is performed during hip arthroscopic surgery in young adult patients with hip pain to improve intraoperative visualization. The stability of the hip joint after anterior capsulectomy is relatively unknown. PURPOSE: To evaluate anterior hip stability in capsular sectioned states with a labral injury to test whether the load required for anterior translation would decrease with greater capsular injuries. STUDY DESIGN: Controlled laboratory study. METHODS: Sixteen hips from 8 of 10 human cadaveric pelvises (mean age, 54.25 years) were prepared/mounted onto a custom-built fixture and tested in 5 states: intact capsule, intact labrum (all intact); sutured capsule, intact labrum (sutured intact); sutured capsule, 1-cm partial labrectomy (sutured labrectomy); partial capsulectomy, 1-cm partial labrectomy (partial capsulectomy); and total capsulectomy, 1-cm partial labrectomy (total capsulectomy). Each hip was tested in a neutral position with a 20-N compressive force. The load at 12 mm of anterior translation was recorded for each state after 2 preconditioning trials. RESULTS: A repeated-measures analysis of variance with Bonferroni adjustment showed no difference between the all-intact versus sutured-intact states and demonstrated no significant difference between the sutured-intact and sutured-labrectomy states. There were significant differences between the sutured-labrectomy and partial capsulectomy (P = .01), sutured-labrectomy and total capsulectomy (P < .001), and partial capsulectomy and total capsulectomy (P = .04) states. CONCLUSION: The findings demonstrate that the capsule/labrum plays an important role in anterior hip stability and that the iliofemoral ligament is crucial for preventing anterior translation in labral-injured states. In addition, the ischiofemoral and pubofemoral ligaments provide resistance to anterior translation in iliofemoral- and labral-deficient states. Intraoperative capsulectomy should be avoided in patients with large, irreparable labral tears to prevent postoperative anterior hip instability. CLINICAL RELEVANCE: This study quantifies the roles of the capsulolabral structures in anterior hip stability and demonstrates the importance of maintaining/repairing them during hip arthroscopic surgery.

Does Repair of a Hill-Sachs Defect Increase Stability at the Glenohumeral Joint?

BACKGROUND: The effect of osteoallograft repair of a Hill-Sachs lesion and the effect of allograft fit on glenohumeral translations in response to applied force are poorly understood. PURPOSE: To compare the impact of a 25% Hill-Sachs lesion, a perfect osteoallograft repair (PAR) of a 25% Hill-Sachs lesion, and an "imperfect" osteoallograft repair (IAR) of a 25% Hill-Sachs lesion on glenohumeral translations in response to a compressive load and either an anterior or posterior load in 3 clinically relevant arm positions. STUDY DESIGN: Controlled laboratory study. METHODS: A robotic/universal force-moment sensor testing system was used to apply joint compression (22 N) and an anterior or posterior load (44 N) to cadaveric shoulders (n = 9) with the skin and deltoid removed (intact) at 3 glenohumeral joint positions (abduction/external rotation): 0°/0°, 30°/30°, and 60°/60°. The 25% bony defect state, PAR state, and IAR state were created and the loading protocol was performed. Translational motion was measured in each position for each shoulder state. A nonparametric repeated-measures Friedman test with a Wilcoxon signed-rank post hoc test was performed to compare the biomechanical parameters (P < .05). RESULTS: Compared with the defect shoulder, the PAR shoulder had significantly less anterior translation with an anterior load in the 0°/0° (15.3 ± 8.2 vs 16.6 ± 9.0 mm, P = .008) and 30°/30° (13.6 ± 7.1 vs 14.2 ± 7.0 mm, P = .021) positions. Compared with IAR, the PAR shoulder had significantly less anterior translation with an anterior load in the 0°/0° (15.3 ± 8.2 vs 16.6 ± 9.0 mm, P = .008) and 30°/30° (13.6 ± 7.1 vs 14.4 ± 7.1 mm, P = .011) positions, and the defect shoulder had significantly less anterior translation with an anterior load in the 30°/30° (14.2 ± 7.0 vs 14.4 ± 7.0 mm, P = .038) position. CONCLUSION: PAR resulted in the least translational motion at the glenohumeral joint. The defect shoulder had significantly less translational motion at the joint compared with the IAR. An IAR resulted in the most translational motion at the glenohumeral joint. This demonstrates the biomechanical importance of performing an osteoallograft repair in which the allograft closely matches the Hill-Sachs defect and fully restores the preinjury state of the humeral head. CLINICAL RELEVANCE: This study demonstrates the importance of performing an osteoallograft repair of a Hill-Sachs defect that closely matches the preinjury state and restores normal humeral head anatomy.

The Influence of Surgical Stabilization on Glenohumeral Abduction Using 3-Dimensional Computed Tomography in Patients With Shoulder Instability.

PURPOSE: This study compared the amount of glenohumeral abduction during arm abduction in the affected and unaffected shoulders of 3 groups of patients with shoulder instability: failed surgical stabilization, successful surgical stabilization, and unstable shoulder with no prior surgical intervention. METHODS: All patients underwent bilateral shoulder computed tomography scans in 3 positions: 0° of abduction and 0° of external rotation (0-0 position), 30° of abduction and 30° of external rotation (30-30 position), and arms maximally abducted (overhead position). Three-dimensional computed tomography reconstruction was performed for both shoulders in all 3 positions. A specialized coordinate system marked specific points and directions on the humerus and glenoid of each model. These coordinates were used to calculate the glenohumeral abduction for the normal and affected sides in the 0-0, 30-30, and overhead positions. RESULTS: Thirty-nine patients with shoulder instability were included, of whom 14 had failed surgical repairs, 10 had successful surgical repairs, and 15 had unstable shoulders with no prior surgical intervention. In the overhead position, patients with failed surgical intervention had significantly less glenohumeral abduction in the failed shoulder (95.6° ± 12.7°) compared with the normal shoulder (101.5° ± 12.4°, P = .02). Patients with successfully stabilized shoulders had significantly less glenohumeral abduction in the successfully stabilized shoulder (93.6° ± 10.8°) compared with the normal shoulder (102.1° ± 12.5°, P = .03). Unstable shoulders with no prior surgical intervention (102.1° ± 10.3°) did not differ when compared with the normal shoulders (101.9° ± 10.9°, P = .95). CONCLUSIONS: Surgical intervention, regardless of its success, limits the amount of abduction at the glenohumeral joint. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Comparison of 3-Dimensional Computed Tomography-Based Measurement of Glenoid Bone Loss With Arthroscopic Defect Size Estimation in Patients With Anterior Shoulder Instability.

PURPOSE: The purpose of this study was to compare four 3-dimensional (3D) computed tomography (CT) methods of measuring glenoid bone loss with the arthroscopic estimation of glenoid bone loss. METHODS: Twenty patients with recurrent anterior shoulder instability underwent bilateral shoulder CT scans and were found to have glenoid bone loss. Arthroscopic estimation of glenoid bone loss was performed in all patients. Three-dimensional CT reconstruction was performed on the CT scans of each patient. The glenoid bone loss of each patient was measured using the surface area, Pico, ratio, and anteroposterior distance-from-bare area methods. The mean percent loss calculated with each method was compared with arthroscopy to determine the reliability of arthroscopy in the measurement of glenoid bone loss. RESULTS: The mean percent bone loss calculated with arthroscopic estimation, surface area, Pico, ratio, and anteroposterior distance-from-bare area methods was 18.13% ± 11.81%, 12.15% ± 8.50% (P = .005), 12.77% ± 8.17% (P = .002), 9.50% ± 8.74% (P < .001), and 12.44% ± 10.68% (P = .001), respectively. Repeated-measures analysis of variance showed that the 3D CT methods and arthroscopy were significantly different (F4,76 = 13.168, P = .02). The estimate using arthroscopy is 55% greater than the average of the 3D CT methods. CONCLUSIONS: Our findings suggest that arthroscopy significantly overestimates glenoid bone loss compared with CT and call into question its validity as a method of measurement. A more internally consistent and accurate method for the measurement of glenoid bone loss is necessary to appropriately diagnose and treat shoulder instability. LEVEL OF EVIDENCE: Level IV, case series.

Nonsurgical management and postoperative rehabilitation of medial instability of the knee.

The medial ligaments of the knee are the most frequently injured structures of the knee joint. The decisions regarding the treatment of medial knee injuries must take into account the severity of injury to the entire knee, the chronicity of the injury, and the patient goals and activity level. The treatment and rehabilitation of the medial structures of the knee is largely reliant on the healing potential of these structures. Studies have shown that these medial, extra-articular ligaments may possess the ability to heal by both intrinsic and extrinsic properties. The goals of nonoperative treatment should include healing of the injured medial structures while controlling edema, restoring full knee motion, and preserving muscle strength. In cases of continued medial instability after an isolated grade III injury or in cases of combined multiligamentous knee injuries, the medial structures of the knee may be treated operatively with repair or reconstruction. The goals of rehabilitation following surgical intervention are the same as for nonoperative treatment; however, the progression of activity is more gradual to allow for repaired or reconstructed tissue to heal. If the objectives of early edema control, restoration of knee motion, gradual resumption of weight bearing, and return of muscle strength are followed, patients should return to full activity following medial injuries to the knee.

Prevalence of the acetabular sublabral sulcus at MR arthrography in patients under 17 years of age: does it exist?

PURPOSE: To retrospectively determine characteristics of contrast-filled acetabular labral clefts in patients under the age of 17 years at MR arthrography (Mra) correlated with arthroscopy, which may impact the thinking regarding the existence of a sublabral sulcus. MATERIALS AND METHODS: After IRB approval, 41 patients under the age of 17 who had MRa were identified. The following observations of contrast-filled clefts were assessed: (1) presence/absence, (2) location, (3) depth, (4) abnormal signal within the labrum and (5) shape (linear, gaping, complex). Fisher's exact and the Wilcoxon matched-pairs signed-rank test were performed. Interreader agreement was calculated with Cohen's k. RESULTS: Reader 1 found clefts in 41 %. Depth was less than half in 6%, more than half in 65% and full thickness in 29%. Shape was linear in 53%, gaping in 18% and complex in 29%. Signal changes occurred in 88%. Reader 2 found clefts in 29%. Depth was less than half in 17%, more than half in 58% and full thickness in 25%. Shape was linear in 50%, gaping in 42% and complex in 17%. Signal changes occurred in 50%. None of the clefts fulfilled the criteria for a sublabral sulcus at MRa and arthroscopy. CONCLUSION: None of the clefts found in our subjects under the age of 17 years met the MRa and arthroscopy criteria for a sublabral sulcus, which supports the theory that such clefts represent labral tears.

Is the all-arthroscopic tibial inlay double-bundle PCL reconstruction a viable option in multiligament knee injuries?

BACKGROUND: All-arthroscopic tibial inlay double-bundle (DB) posterior cruciate ligament (PCL) reconstruction avoids an open dissection and the "killer turn" while maintaining the advantage of an anatomic graft. However, clinical data on the viability of this surgical technique in multiligamentous knee injuries are lacking. QUESTIONS/PURPOSES: At greater than 2 years of followup, we evaluated (1) validated outcomes scores; (2) range of motion; and (3) side-to-side stability on PCL stress radiographs of a small group of patients who underwent all-arthroscopic tibial inlay DB PCL reconstruction in multiligamentous knee injuries, either shortly after injury or late. METHODS: All patients sustaining an operative multiligamentous knee injury between August 2007 and March 2009 underwent PCL reconstruction with the all-arthroscopic tibial inlay DB PCL reconstruction. Twelve patients sustained such injuries and were reconstructed during the study period and all 12 returned for followup with a minimum of 2 years (mean 3 ± 0.8 years). There were nine males and three females, with a mean age of 30 years; four patients had a subacute reconstruction (≥ 3 weeks, but < 3 months), and eight patients had chronic reconstructions (> 3 months). Mean time from injury to PCL reconstruction was 7 ± 12 months. Demographics, ROM, outcome scores (Lysholm and International Knee Documentation Committee [IKDC] scores), and PCL stress views were obtained. RESULTS: At final followup, mean Lysholm and IKDC subjective scores were 79 ± 16 and 72 ± 19, respectively. IKDC objective scores included eight nearly normal knees, three abnormal knees, and one severely abnormal knee. Mean flexion and extension losses compared with the contralateral were 10 ± 9 and 1 ± 2, respectively. Mean ± SD final side-to-side difference on PCL stress radiographs was 5 ± 3 mm. CONCLUSIONS: The clinical and radiographic results of the all-arthroscopic tibial inlay DB PCL reconstruction appear comparable to the same technique in isolated PCL injuries and, based on similar published case series, comparable to results of multiligamentous knee reconstructions using other PCL reconstruction techniques. LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.

An increase in cranial acetabular version with age: implications for femoroacetabular impingement.

This cadaveric study aimed to determine if acetabular retroversion demonstrates predictable changes with age that could inform understanding of factors that may contribute to the pathophysiology of femoroacetabular impingement. Two-hundred forty pelves were divided into young and old groups. Version was measured at the cranial (5mm below superior rim), central (transverse of acetabulum), and caudal (5mm above inferior rim) locations. The data showed a significant difference between young (10±10°) and old (13±9°) cranial version (P=.02). Cranial retroversion increases with age and may reflect a developmental component in the etiology of the focal rim impingement lesion or ossification of the damaged labrum. Global acetabular retroversion does not appear to change with age and may reflect a congenital etiology.

Comparison of reconstructive procedures for glenoid bone loss associated with recurrent anterior shoulder instability.

HYPOTHESIS: A tibial plafond allograft, iliac crest allograft, and coracoid autograft in a congruent arc Latarjet reconstruction better restore radius of curvature, depth, and surface area for glenoid bone loss in recurrent instability compared with the coracoid autograft in a standard Latarjet reconstruction for anteroinferior glenoid bone loss of the shoulder. METHODS: Three-dimensional shoulder models were generated from bilateral computed tomography scans in 15 patients, who were a mean (standard deviation [SD]) age of 23 (7.7) years, with recurrent anterior shoulder instability and known glenoid bone loss. The surface areas of the glenoid in the involved and contralateral normal shoulder were measured. Virtual surgery was then performed using standard and congruent arc Latarjet reconstruction, tibial plafond, and iliac crest allografts. Grafts were optimally positioned to restore articular congruity and defect fill. Radius of curvature and restoration of glenoid depth were compared with the contralateral glenoid. RESULTS: Glenoid surface area (11.04% [6.95% SD]) and depth (0.75 [0.57 SD] vs 1.44 [0.65 SD] mm) were significantly reduced (P < .012) in the injured glenoid. The mean (SD) coronal plane radius of curvature of the congruent arc Latarjet reconstruction (60.3 [39.0 SD] mm) more closely matched the radius of curvature of the injured glenoid (67.5 [33.2 SD] mm) compared with the other grafts. Restored glenoid depth was greater in the tibial plafond (1.8 [1.1 SD] mm) and iliac crest (2.0 [0.6 SD] mm) allografts compared with other grafts (P < .002). CONCLUSION: Congruent arc Latarjet reconstruction more closely restores native glenoid coronal radius of curvature, whereas tibial plafond and iliac crest allografts more adequately restore depth compared with standard Latarjet reconstruction.

A biomechanical analysis of the soft tissue and osseous constraints of the hip joint.

PURPOSE: The goal of this study was to determine the role of soft tissue and osseous constraints in hip biomechanics using a unique robotic testing apparatus. METHODS: Four fresh-frozen human cadaveric hemi-pelvises without degenerative changes or dysplasia were stripped of all soft tissue except the ligamentous capsule and the intra-articular structures. All hips were tested using a robotic manipulator/universal force-moment sensor testing system to measure and compare end-range of motion (ROM) and kinematic translations in "capsule vented" (a small hole in the capsule) and "capsule separated" (capsular ligaments separated from each other) states. Then, the "capsule vented" state was compared to the condition in which the capsule and labrum were removed to calculate bone and soft tissue forces with 40 N of load applied in six different directions along three axes. RESULTS: There were no significant differences in end-ROM or kinematic translations between the "capsule vented" and "capsule separated" states. Bone forces significantly increased with loads applied in the anterior, posterior and superior directions. Soft tissue forces increased significantly with loads applied in the medial, lateral and inferior directions. CONCLUSION: The individual hip capsular ligaments act independently of each other to resist end-ROM. Both osseous and soft tissue constraints are important to hip biomechanics depending upon the direction of applied force. The clinical relevance is that surgical management for hip disorders should preserve the soft tissue constraints in the hip when possible to maintain normal hip biomechanics.

Gender and racial differences in focal and global acetabular version.

The purpose of this study was to compare the acetabular version between male and female pelvises. We hypothesized that female acetabula would demonstrate more retroversion because Pincer-type femoroacetabular impingement (FAI) is associated with acetabular retroversion, which is more commonly observed in females. 120 bony pelvic specimens were randomly collected. The version was measured at three different axial sections of each acetabulum: cranial, central, and caudal. Males demonstrated significantly less anteversion than females in every section. The global version (the average of all three measurements) was also significantly different between males and females (16° ± 7° and 19° ± 8° respectively, P<0.001). Of the 240 examined acetabuli, 21 demonstrated cranial retroversion (16 males & 5 females). The data showed no significant difference (P=0.353) between global version of African Americans (18° ± 9°) and Caucasians (17° ± 7°). The results of this study suggest that symptomatic FAI in the female population likely reflects a complex interplay of femoral and acetabular dysmorphology and cannot be explained by differences in acetabular version alone.

Rotator cuff tear and glenohumeral instability : a systematic review.

BACKGROUND: The rotator cuff plays a significant role in the static and dynamic stability of the glenohumeral joint. Rotator cuff tears may occur after shoulder dislocations, whether in younger athletes or older patients with age-related tendon degeneration. Untreated tears may cause persistent pain, dysfunction, instability, and degenerative changes. A thorough understanding of when to look for rotator cuff tears after shoulder dislocations and how best to manage them may decrease patients' pain and improve function. QUESTIONS/PURPOSES: We systematically reviewed the available literature to better understand (1) when a rotator cuff tear should be suspected after a dislocation, (2) whether surgical or nonsurgical approaches result in better scores for pain and satisfaction in patients with rotator cuff tears resulting from shoulder dislocations, and (3) whether intraarticular lesions, rotator cuff tears, or both should be addressed when surgery is performed. METHODS: We systematically searched MEDLINE(®), CINAHL, and EMBASE for studies published from 1950 to 2012. We included studies reporting outcomes after treatment in patients with rotator cuff tears and shoulder dislocations. We excluded case reports, studies without any treatment, and studies about patients treated with arthroplasty. Five Level III and six Level IV studies were ultimately selected for review. RESULTS: Patients with persistent pain or dysfunction after a shoulder dislocation often had a concomitant rotator cuff tear. Surgical repair resulted in improved pain relief and patient satisfaction compared to nonoperative management. Repair of the rotator cuff, along with concomitant capsulolabral lesions, helped restore shoulder stability. While these findings are based on Level III and IV evidence, better long-term studies with larger cohorts are needed to strengthen evidence-based recommendations. CONCLUSIONS: Persistent pain and dysfunction after a shoulder dislocation should prompt evaluation of the rotator cuff, especially in contact or overhead athletes, patients older than 40 years, or those with nerve injury. Surgery should be considered in the appropriately active patient with a rotator cuff tear after dislocation. While the current literature suggests improved stability and function after surgical repair of the rotator cuff, higher-quality prospective studies are necessary to make definitive conclusions.

Characterization of Human Anterosuperior Acetabular Depression in Correlation With Labral Tears.

BACKGROUND: Labral tears often occur in the same quadrant of the acetabulum at a small depression previously referred to as the psoas valley. Understanding the anatomic variations of this depression could help us understand the etiology of labral tears. PURPOSE: To describe the location and dimensions of the depression located in the anterosuperior acetabular rim. The hypothesis was that the location of this depression would be consistent with the common location of acetabular labral tears described in the literature. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 240 pelvic specimens were divided into 2 groups (n = 120 for each) according to age (younger age group: 21.36 ± 3.12 years [range, 14-24 years]; older age group: 42.30 ± 10.27 years, [range, 25-60 years]).Specimens were also categorized based on sex (mean age: 31.93 ± 12.31 years [male]; 32.08 ± 13.66 years [female]) and race (mean age: 31.45 ± 13.16 years [black]; 32.57 ± 12.82 years [white]). The depth and width of the acetabular depression were measured using a digital caliper, and the location was measured using a goniometer. RESULTS: The psoas valley was observed in every specimen and was located in the anterosuperior quadrant of the acetabulum. Its depth was significantly greater (P < .001) in males (5.35 ± 1.60 mm) than in females (3.95 ± 1.31 mm). The width of the psoas valley was also greater (P < .001) in males (29.39 ± 3.98 mm) than in females (24.49 ± 4.80 mm). There were no differences in size or location of the depression between races or age groups. The psoas valley was located between 3.92 ± 0.42 o'clock anteriorly and 2.12 ± 0.77 o'clock posteriorly. CONCLUSION: The differences observed in the study data are believed to be a result of the different anatomic morphologies of the pelvis in males and females. This loss of bony support, caused by the depression, could be the underlying cause of weakening of the acetabular labrum as people age. CLINICAL RELEVANCE: The loss of bony support in the anterosuperior acetabular depression could contribute to the labral tears that commonly occur in this area. Understanding the normal anatomy of this area could be important in determining the risk of labral tears as well as treatment options.

Posterior shoulder instability in the contact athlete.

Historically, posterior shoulder instability has been a challenging problem for contact athletes and orthopedic surgeons alike. A complete understanding of the normal shoulder anatomy and biomechanics and the pathoanatomy responsible for the instability is necessary for a successful clinical outcome. In addition, the surgeon must be familiar with the diagnostic imaging and physical examination maneuvers required for the correct diagnosis without missing any other concurrent abnormalities. This understanding will allow orthopedists to plan and execute the appropriate management, whether this may involve conservative or surgical intervention. The goal should always be to correct the abnormality and have the patient return to play with full strength and no recurrent instability.

Capsular laxity of the hip: findings at magnetic resonance arthrography.

PURPOSE: The purpose of this study was to retrospectively investigate magnetic resonance (MR) arthrography imaging findings associated with capsular laxity of the hip joint found at surgery. METHODS: After institutional review board approval, 27 patients who had arthroscopy reports that described the presence or absence of capsular laxity of the hip joint were identified over a 2-year period. Preoperative MR images were retrospectively reviewed by 2 blinded radiologists. The following observations were recorded: (1) thickness, signal intensity, and defects of the anterior joint capsule; (2) thickness and signal intensity of the zona orbicularis; (3) width of the anterior and posterior joint recesses at the level of the femoral head; (4) presence of synovitis in the anterior joint recess; and (5) volume of intra-articular contrast and degree of hip rotation. Intrarater and inter-rater agreement was assessed. RESULTS: Of the 27 patients, 17 were positive and 10 were negative for hip joint laxity at arthroscopy. The mean thickness of the anterior hip capsule was significantly different (P = .0043), measuring 2.5 mm (95% confidence interval [CI], 2.3 to 2.8 mm) in those with hip laxity and 3.3 mm (95% CI, 2.8 to 3.8 mm) in those without laxity. The mean width of the anterior joint recess was 5.8 mm (95% CI, 5.4 to 6.3 mm) in those with laxity and 3.6 mm (95% CI, 3.3 to 3.9 mm) in those without laxity and was significantly different (P < .0001). No other variables were considered useful because of a lack of significant differences between the 2 patient groups or low inter-rater agreement. CONCLUSIONS: On the basis of 95% CIs, hip joint laxity at MR arthrography is associated with widening of the anterior hip joint recess (>5 mm) and thinning of the adjacent joint capsule (<3 mm) lateral to the zona orbicularis.

Femoroacetabular cam-type impingement: global assessment of the femoral head-neck junction on a single reformatted MR image.

PURPOSE: To characterize the imaging appearance of femoral head-neck contour abnormalities on a short-axis magnetic resonance (MR) image compared with the usual anterior alpha angle measurements and multiple alpha angle measurements on radial reformatted MR images, with surgery as the reference standard. MATERIALS AND METHODS: After institutional review board approval of this HIPAA-compliant study, 21 patients who underwent arthroscopy and 24 patients who did not, all of whom were evaluated with three-dimensional MR imaging, during 1 year were identified. Short-axis MR images of the femoral head-neck junction were reformatted with multiple radial images along the axis of the femoral neck. The following measurements were made at each hour of a clock face: (a) presence and size of bone contour abnormality visible beyond a best-fit circle and (b) femoral head-neck offset angles. Mann-Whitney, Fisher exact, and Wilcoxon matched-pair signed rank tests were performed. Intra- and interreader agreement were calculated as the Cohen κ. RESULTS: Of the 21 subjects who underwent surgery, 16 were confirmed to have cam-type femoroacetabular impingement (FAI) at surgery. Comparing findings from short-axis images with those at surgery, average accuracy was 81%. Comparing findings from head-neck offset angles with those at surgery, average accuracy was 80%. On short-axis images, average bone elevation was 3.2 mm in patients with cam-type FAI and 1.4 mm in those without it. In eight of 24 subjects who did not undergo surgery, the alpha angle was normal but the short-axis MR image showed abnormal bone contour. CONCLUSION: An abnormal bone contour identified on a short-axis MR image at the femoral head-neck junction correlates with surgical findings and may allow for a global characterization of the bone abnormality with regard to location, extent, and amount of elevation compared with the alpha angle and multiple head-neck offset angles.