Snapping scapula syndrome: diagnosis and management.

Scapulothoracic bursitis and snapping scapula syndrome are rare diagnoses that contribute to considerable morbidity in some patients. These conditions represent a spectrum of disorders characterized by pain with or without mechanical crepitus. They are commonly identified in young, active patients who perform repetitive overhead activities. Causes include anatomic scapular or thoracic variations, muscle abnormalities, and bony or soft-tissue masses. Three-dimensional CT and MRI aid in detecting these abnormalities. Nonsurgical therapy is the initial treatment of choice but is less successful than surgical management in patients with anatomic abnormalities. In many cases, scapular stabilization, postural exercises, or injections eliminate symptoms. When nonsurgical treatment fails, open and endoscopic techniques have been used with satisfactory results. Familiarity with the neuroanatomic structures surrounding the scapula is critical to avoid iatrogenic complications. Although reported outcomes of both open and endoscopic scapulothoracic decompression are encouraging, satisfactory outcomes have not been universally achieved.

Biomechanical analysis of two-tendon posterosuperior rotator cuff tear repairs: extended linked repairs and augmented repairs.

PURPOSE: The purpose of this study was to compare single-row (SR), extended double-row (DR), and augmented, extended double-row (aDR) rotator cuff repairs in a two-tendon, posterosuperior rotator cuff tear (RCT) model with intact rotator cuff tendons. METHODS: RCTs were created and randomly assigned to SR, DR, or aDR repair (5 each) in 20 cadaveric shoulder specimens. A collagen scaffold was used for augmentation. In the remaining 5 specimens, the rotator cuffs were left intact. All specimens were cyclically loaded from 25 to 75 N for 50 cycles. Every 50 cycles, peak load was increased by 25 N until failure occurred. Cyclic stiffness and number of cycles were analyzed. RESULTS: The SR (72.9 ± 4.64 N/mm)- and aDR (72.6 ± 11.8 N/mm)-repaired specimens differed significantly in stiffness from the intact specimens (93.1 ± 14.8 N/mm) at ≥100 N (P < .05). The intact specimens and DR- and aDR-repaired specimens endured more cycles to failure (1,556 ± 677, 1,302 ± 248, and 1,211 ± 95, respectively) than the SR-repair specimens (388 ± 72 cycles, 260 ± 4 N) (P < .05 for all groups). CONCLUSIONS: Linked DR constructs were significantly stronger than SR repairs in this two-tendon RCT model and approached the strength of the intact rotator cuff. Augmentation with a collagen patch (aDR) did not influence biomechanical repair qualities in this model, but did result in less variability in failure load and more consistency in the mode of failure. CLINICAL RELEVANCE: The biomechanical properties of extended linked DR constructs are superior to those of SR constructs for repair of two-tendon RCTs, and are not compromised by graft augmentation.

Reconstruction of posterior glenoid deficiency using distal tibial osteoarticular allograft.

Posterior shoulder instability with glenoid deficiency is a rare entity and its surgical treatment is challenging. Reconstructive techniques have focused on extra-articular structural bone transfer that obstructs humeral translation and thereby prevents glenohumeral dislocation. However, long-term results are not as promising. In this report, the authors describe a technique for anatomic posterior glenoid reconstruction using an osteoarticular distal tibia allograft in two patients including their outcomes after 2 years. Level of evidence IV.

Management of clavicle nonunion and malunion.

BACKGROUND: Clavicle fractures are common injuries of the shoulder girdle and occasionally result in nonunion or symptomatic malunion. When present, these chronic injuries can result in considerable shoulder dysfunction. A number of surgical techniques have been described for the management of these injuries. Current literature suggests that supplemental bone grafting may not be necessary in all cases but should be considered in the setting of atrophic nonunion. However, optimal treatment is controversial, as discussed in the literature. This article highlights the current treatment options based on the existing literature and describes our preferred techniques. METHODS: We carried out a comprehensive review of the PubMed and Medline databases using multiple keywords (eg, clavicle fracture, clavicle nonunion, and clavicle malunion) to identify the relevant literature regarding this topic. Reference lists of the relevant articles were reviewed for additional important articles. CONCLUSION: Nonunion and malunion of the clavicle remain challenging problems. Reliable bony union and improved shoulder function can be expected with thoughtful surgical planning, appropriate implant choice, and meticulous surgical technique.

An association between the inferior humeral head osteophyte and teres minor fatty infiltration: evidence for axillary nerve entrapment in glenohumeral osteoarthritis.

BACKGROUND: Glenohumeral osteoarthritis often results in inferior humeral osteophytes. Anatomic studies suggest that the axillary neurovascular bundle is in close proximity to the glenohumeral capsule. We therefore hypothesize that an inferior humeral osteophyte of sufficient magnitude could encroach on the axillary nerve and result in measurable fatty infiltration of the teres minor muscle. MATERIALS AND METHODS: Preoperative magnetic resonance imaging studies of 91 consecutive arthritic shoulders were retrospectively reviewed. Two cohorts were established based on the presence of a humeral osteophyte. The distances from the axillary neurovascular bundle to various osseous structures were measured using calibrated software. Objective quantitative measurements of the degree of fatty infiltration of the teres minor muscles were obtained with image analysis software. Results were compared between cohorts. RESULTS: The distance between the inferior humerus and axillary neurovascular bundle was inversely correlated to the size of the inferior humeral osteophyte (ρ = -0.631, P < .001). Fatty infiltration of the teres minor was greater when an inferior osteophyte was present (11.9%) than when an osteophyte was not present (4.4%) (P = .004). A statistically significant correlation between the size of the humeral head spur and quantity of fat in the teres minor muscle belly (ρ = 0.297, P = .005) was identified. CONCLUSION: These data are consistent with our hypothesis that the axillary nerve may be entrapped by the inferior humeral osteophyte often presenting with glenohumeral osteoarthritis. Entrapment may affect axillary nerve function and lead to changes in the teres minor muscle. Axillary neuropathy from an inferior humeral osteophyte may represent a contributing and treatable cause of pain in patients with glenohumeral osteoarthritis.

Technique and outcomes of arthroscopic scapulothoracic bursectomy and partial scapulectomy.

PURPOSE: The purpose of this study was to assess the efficacy of arthroscopic scapulothoracic bursectomy in patients with snapping scapula syndrome with a minimum of 2 years' follow-up. METHODS: In this institutional review board-approved retrospective study, 23 shoulders in 21 consecutive patients were identified that had undergone arthroscopic treatment of snapping scapula syndrome. Each patient described mechanical symptoms with failure of nonsurgical modalities and reported symptomatic relief from a local anesthetic injection before surgical intervention. Preoperative and postoperative pain and functioning levels were assessed with the American Shoulder and Elbow Surgeons (ASES), QuickDASH (shortened version of the Disabilities of the Arm, Shoulder and Hand questionnaire), and Single Assessment Numeric Evaluation (SANE) shoulder scores, and patient satisfaction was recorded on a 10-point visual analog scale. Univariate and paired t tests were used for data analysis. Significance was established at P ≤ .05. RESULTS: The mean age at the time of surgery was 33 years (SD, 14 years). A scapulothoracic bursectomy alone was performed in 2 shoulders, and the remaining 21 shoulders underwent both bursectomy and scapuloplasty of the superomedial or inferomedial scapular border. At a mean follow-up of 2.5 years (SD, 0.57 years), a significant improvement in the median ASES score was noted, from 53 points (range, 17 to 83 points) preoperatively to 73 points (range, 32 to 100 points) postoperatively (P = .001). The mean SANE and QuickDASH scores at follow-up were 73 (SD, 27) and 35 (SD, 30), respectively. Overall, median patient satisfaction with surgical outcome was 6 of 10 (range, 1 to 10). Of the shoulders, 3 (13%) underwent revision for persistent scapulothoracic pain. CONCLUSIONS: Snapping scapula syndrome can be a debilitating disorder. Although significant pain and functional improvement can be expected after arthroscopic bursectomy and scapuloplasty, the average postoperative ASES and SANE scores remain lower than expected. LEVEL OF EVIDENCE: Level IV, retrospective case series.

Surgical anatomy of the shoulder.

The glenohumeral articulation is a versatile joint that requires a complex integration of bony ligamentous, musculotendinous, and neurovascular structures for proper function. Injuries resulting from dysfunction are common and potentially debilitating. Many of these injuries can be managed nonsurgically; however, if surgical treatment is indicated, a thorough knowledge of the anatomy of the shoulder girdle is critical. It is important for the surgeon to be aware of commonly used arthroscopic and surgical approaches to the glenohumeral joint along with anatomic structures at risk with each surgical approach and methods of avoiding injury.

Treatment of clavicle fractures: current concepts review.

Clavicle fractures are common in adults and children. Most commonly, these fractures occur within the middle third of the clavicle and exhibit some degree of displacement. Whereas many midshaft clavicle fractures can be treated nonsurgically, recent evidence suggests that more severe fracture types exhibit higher rates of symptomatic nonunion or malunion. Although the indications for surgical fixation of midshaft clavicle fractures remain controversial, they appear to be broadening. Most fractures of the medial or lateral end of the clavicle can be treated nonsurgically if fracture fragments remain stable. Surgical intervention may be required in cases of neurovascular compromise or significant fracture displacement. In children and adolescents, these injuries mostly consist of physeal separations, which have a large healing potential and can therefore be managed conservatively. Current concepts of clavicle fracture management are discussed including surgical indications, techniques, and results.

Management of multidirectional instability of the shoulder.

Multidirectional shoulder instability is defined as symptomatic instability in two or more directions. Instability occurs when static and dynamic shoulder stabilizers become incompetent due to congenital or acquired means. Nonspecific activity-related pain and decreased athletic performance are common presenting complaints. Clinical suspicion for instability is essential for timely diagnosis. Several examination techniques can be used to identify increased glenohumeral translation. It is critical to distinguish increased laxity from instability. Initial management begins with therapeutic rehabilitation. If surgical management is required, capsular plication has been used successfully. Advanced arthroscopic techniques offer several advantages over traditional open approaches and may have similar outcomes. The role of rotator interval capsular plication is controversial, but it may be used to augment capsular plication in patients with specific patterns of instability. Despite encouraging results, outcomes remain inferior to those associated with traumatic unidirectional instability.

Multimedia article. The rotator interval: pathology and management.

The rotator interval describes the anatomic space bounded by the subscapularis, supraspinatus, and coracoid. This space contains the coracohumeral and superior glenohumeral ligament, the biceps tendon, and anterior joint capsule. Although a definitive role of the rotator interval structures has not been established, it is apparent that they contribute to shoulder dysfunction. Contracture or scarring of rotator interval structures can manifest as adhesive capsulitis. It is typically managed nonsurgically with local injections and gentle shoulder therapy. Recalcitrant cases have been successfully managed with an arthroscopic interval release and manipulation. Conversely, laxity of rotator interval structures may contribute to glenohumeral instability. In some cases this can be managed with one of a number of arthroscopic interval closure techniques. Instability of the biceps tendon is often a direct result of damage to the rotator interval. Damage to the biceps pulley structures can lead to biceps tendon subluxation or dislocation depending on the structures injured. Although some authors describe reconstruction of this tissue sling, most recommend tenodesis or tenotomy if it is significantly damaged. Impingement between the coracoid and lesser humeral tuberosity is a relatively well-established, yet less common cause of anterior shoulder pain. It may also contribute to injury of the anterosuperior rotator cuff and rotator interval structures. Although radiographic indices are described, it appears intraoperative dynamic testing may be more helpful in substantiating the diagnosis. A high index of suspicion should be used in association with biceps pulley damage or anterosuperior rotator cuff tears. Coracoid impingement can be treated with either open or arthroscopic techniques. We review the anatomy and function of the rotator interval. The presentation, physical examination, imaging characteristics, and management strategies are discussed for various diagnoses attributable to the rotator interval. Our preferred methods for treatment of each lesion are also discussed.

Arthroscopic trans-capsular axillary nerve decompression: indication and surgical technique.

Symptomatic axillary nerve compression is rare yet results in debilitating pain, weakness, and decreased athletic performance in some patients. If nonoperative modalities fail, surgical intervention is necessary to reduce symptoms and avoid functional decline. Traditionally, open techniques have been described to decompress the axillary nerve and are reported to provide satisfactory results. Similar to suprascapular nerve decompression, recent advances have provided the opportunity to develop all-arthroscopic axillary nerve decompression techniques. Although direct comparisons between open and arthroscopic techniques do not exist, arthroscopic axillary nerve decompression may provide some benefits over open techniques. Therefore we present a technique and early results for all-arthroscopic trans-capsular axillary nerve decompression.

Arthroscopic management of glenohumeral arthrosis: humeral osteoplasty, capsular release, and arthroscopic axillary nerve release as a joint-preserving approach.

Glenohumeral arthrosis frequently results in substantial discomfort and activity limitations. Shoulder arthroplasty has been shown to provide reliable pain relief under these circumstances in older, less active populations. Younger patients, however, who desire to continue participation in high-demand activities, may not be optimal candidates for glenohumeral arthroplasty. Arthroscopic debridement has been reported to provide incomplete symptomatic relief in this cohort of patients. It is evident from cadaveric studies that the axillary nerve runs in close proximity to the inferior glenohumeral capsule. An inferior humeral osteophyte of sufficient size may compress the axillary nerve and potentially contribute to posterior shoulder pain in a manner similar to quadrilateral space syndrome. Therefore we present a technique for and early results of the arthroscopic management of glenohumeral arthrosis in young, high-demand patients. This technique combines traditional glenohumeral debridement and capsular release with inferior humeral osteoplasty and arthroscopic transcapsular axillary nerve decompression. In the appropriate patient, these additions may provide symptomatic relief that is greater than that with simple debridement alone.

Technical aspects of anterior cruciate ligament reconstruction for the general orthopaedic surgeon.

Anterior cruciate ligament reconstruction is the sixth most common procedure performed by orthopaedic surgeons. The goals of the procedure are to restore knee stability and patient function. These goals are dependent on proper graft positioning and incorporation. Anterior cruciate ligament reconstruction involves a technically complicated series of steps, all of which affect graft healing and clinical outcome. A wide variety of graft choices and surgical techniques are currently available for use. It is important for orthopaedic surgeons performing anterior cruciate ligament reconstructions to be aware of the indications for graft selection, techniques for correct graft placement, and the biologic implications related to these factors.

Van neck disease: osteochondrosis of the ischiopubic synchondrosis.

BACKGROUND: Van Neck disease (VND) is a benign skeletal abnormality of children involving a hyperostosis of the ischiopubic synchondrosis (IPS) seen on radiographs. Patients typically complain of vague groin or buttock pain. Few descriptions of this disorder exist and it easily can be mistaken for other entities, particularly osteomyelitis or tumor. It is often considered a diagnosis of exclusion as laboratory values are usually normal and routine radiographic workup may be nonspecific. We present a series of patients with VND and we compare them with a similar cohort of patients with acute hematogenous ischiopubic osteomyelitis (IPOM). We also draw attention to a new magnetic resonance imaging (MRI) finding that seems to support the theory that VND results from an excessive pull of the hamstring tendon on the ischial tuberosity. METHODS: All patients presenting to our institution for the evaluation of groin or buttock pain during an 8-year period (August 2001 to May 2009) were retrospectively identified. Twenty-five patients demonstrated enhancement of the ischiopubic area on MRI. Five patients were excluded for lack of sufficient laboratory data. Ten patients were diagnosed and treated with culture proven IPOM and 10 patients were diagnosed with VND and treated with observation. History, physical examination, laboratory values, plain films, and MRI were compared to identify the diagnostic differences between these 2 entities. RESULTS: The age range for both groups was between 4 and 12 years old. The mean age was 7 years for the VND group and 7.6 years for the IPOM group. The VND group tended to have more distinct hyperostosis of the IPS on radiographs. The factors that were characteristic of IPOM were: fever, limp, pain with rotation of the hip, elevated erythrocyte sedimentation rate, elevated C-reactive protein (CRP), and positive blood culture. MRI showed obvious myositis, abscess, and free fluid surrounding the IPS in all patients with IPOM, but not in the VND patients. Enhancement was seen in the ischial tuberosity, near the hamstring origin, in nearly all Van Neck patients; this pattern of edema may support stress reaction and callus formation as a mechanism for IPS hypertrophy. CONCLUSIONS: VND is a little-known entity characterized by enlargement of the IPS and should be in the differential of groin or buttock pain in children from the age of 4 to 12 years. IPOM may present similar to VND. Absence of fever, limp, pain with rotation of the hip, elevated C-reactive protein/erythrocyte sedimentation rate, and negative blood culture can help to differentiate VND from IPOM. Presence of marrow edema around the IPS and in the ischial tuberosity, along with absence of surrounding myositis, abscess, and free fluid on MRI are reliable findings that can confirm the diagnosis of VND. The absence of these characteristics can eliminate the need for admission, aspiration, or biopsy. The treatment for VND is observation and the symptoms should abate over time with expectant management. LEVEL OF EVIDENCE: Comparative Diagnostic, Level IV.

Acromioclavicular joint injuries: anatomy, diagnosis, and treatment.

Acromioclavicular (AC) joint injuries are common in athletic populations and account for 40% to 50% of shoulder injuries in many contact sports, including lacrosse, hockey, rugby and football. The AC joint is stabilized by static and dynamic restraints, including the coracoclavicular (CC) ligaments. Knowledge of these supporting structures is important when identifying injury and directing treatment. Management of AC injuries should be guided by severity of injury, duration of injury and symptoms, and individual patient factors. These help determine how best to guide management, and whether patients should be treated surgically or nonsurgically. Treatment options for AC injuries continue to expand, and include arthroscopic-assisted anatomic reconstruction of the CC ligaments. The purpose of this article is to review the anatomy, diagnostic methods, and treatment options for AC joint injuries. In addition, the authors' preferred reconstruction technique and outcomes are presented.

Predictors of Revision Surgery After Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Arthroscopically assisted anterior cruciate ligament (ACL) reconstruction is a common orthopaedic procedure. Graft failure after reconstruction remains a devastating complication, often requiring revision surgery and less aggressive or modified rehabilitation. Worse functional and patient-reported outcomes are reported compared with primary reconstruction. Moreover, both rates and risk factors for revision are variable and inconsistent within the literature. PURPOSE: To determine the rate of revision surgery after ACL reconstruction in a large cohort of patients, to assess the influence of patient characteristics on the odds of revision, and to compare revision rates between active-duty military members and non-active-duty beneficiaries. STUDY DESIGN: Descriptive epidemiology study. METHODS: Using administrative data from the Military Health System, a retrospective study was designed to characterize the rate of ACL revision surgery among patients treated within a military facility. All patients ≥18 years at the time of ACL reconstruction were identified using the American Medical Association Current Procedural Terminology (CPT) for ACL reconstruction (CPT code 29888) over 7 years (2005-2011). Revision ACL reconstructions were identified as having ≥2 ACL reconstruction procedure codes on the ipsilateral knee at least 90 days apart. Univariate analysis was performed to calculate odds ratios (ORs) for demographic, perioperative medication use, and concomitant procedure-related risk factors. A multivariate logistic regression model determined risk covariates in the active-duty cohort. RESULTS: The study population consisted of 17,164 ACL reconstructions performed among 16,336 patients, of whom 83.3% were male with a mean ± SD age of 28.9 ± 7.6 years for the nonrevision group, and was predominantly active duty (89.2%). Patients undergoing ACL reconstruction on both knees only contributed their index knee for analyses. There were 587 patients who underwent revision surgery, corresponding to an overall revision rate of 3.6%. The median time from the index surgery to revision surgery was 500 days (interquartile range, 102-2406 days). Revision rates were higher in the active-duty cohort as compared with non-active-duty beneficiaries (3.8% vs 1.8%, respectively; OR, 2.14; 95% CI, 1.49-3.07). Based on multivariate logistic regression in the active-duty cohort, age ≥35 years (OR, 0.44; 95% CI, 0.33-0.58) and concomitant meniscal repair (OR, 0.69; 95% CI, 0.53-0.91) were found to be protective with regard to the odds of revision surgery. Perioperative medication use of nonsteroidal anti-inflammatory drugs (NSAIDs) (OR, 1.33; 95% CI, 1.12-1.58; number needed to harm [NNH], 100) and COX-2 inhibitors (OR, 1.31; 95% CI, 1.04-1.66; NNH, 333) was associated with increased odds of revision surgery. No significant findings were detected among sex, race, nicotine use, body mass index, or other concomitant procedures of interest. CONCLUSION: In this large cohort study, the rate of revision ACL reconstruction was 3.6%, which is consistent with the existing literature. Increased odds of revision surgery among active-duty personnel were associated with the perioperative use of NSAIDs and COX-2 inhibitors. Age ≥35 years and concomitant meniscal repair were found to be protective against ACL revision.

The Prevalence of Symptomatic Deep Venous Thrombosis and Pulmonary Embolism After Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Arthroscopically assisted anterior cruciate ligament (ACL) reconstruction is a common orthopaedic procedure. The incidence and risk factors of venous thromboembolism (VTE) after ACL reconstruction remain unclear. PURPOSE: To define the incidence of VTE after ACL reconstruction and identify associated risk factors in a large cohort of patients. STUDY DESIGN: Descriptive epidemiological study. METHODS: All patients aged ≥18 years who underwent ACL reconstruction between 2005 and 2011 were identified from the Department of Defense Medical Data Repository. The prevalence of VTE, including deep venous thrombosis (DVT) and pulmonary embolism (PE), within 3 months of ACL reconstruction was queried. Univariate analyses were performed to define odds ratios (ORs) for demographic, medication use, and procedural-related risk factors. RESULTS: A total of 87 VTE events (0.53% [95% CI, 0.42%-0.65%]) occurred after 16,558 ACL reconstructions performed on 15,767 patients. DVT was documented after 55 procedures and PE after 35 procedures. Three patients were documented to have both DVT and PE within the study period. The odds of VTE increased in patients aged ≥35 years (OR, 1.96 [95% CI, 1.27-3.04]; P = .003). Nicotine history increased the odds of DVT (OR, 1.99 [95% CI, 1.15-3.43]; P = .014). Concomitant high tibial osteotomy (HTO) increased the odds of PE (OR, 18.31 [95% CI, 2.4-139.6]; P = .005), whereas concomitant posterior cruciate ligament (PCL) reconstruction increased the odds of both VTE (OR, 3.43 [95% CI, 1.07-11.2]; P = .38) and DVT (OR, 5.57 [95% CI, 1.71-18.14]; P = .004). Nonsteroidal drug use was associated with decreased odds for VTE and DVT (OR, 0.44 [95% CI, 0.28-0.70]; P < .001 and OR, 0.38 [95% CI, 0.22-0.69]; P < .001, respectively). Anticoagulants were associated with increased odds for VTE, DVT, and PE (OR, 98.32 [95% CI, 61.63-156.86]; P < .001; OR, 111.93 [95% CI, 63.95-195.92]; P < .001; and OR, 47.84 [95% CI, 22.55-101.52]; P < .001, respectively). No detectible difference in odds was found for sex, body mass index, or aspirin or cyclooxygenase-2 inhibitor use. CONCLUSION: The incidence of VTE after ACL reconstruction in this large population was low. Increased odds of VTE was identified in patients aged ≥35 years with a history of nicotine use, anticoagulant use, concomitant HTO, or concomitant PCL reconstruction. Controlled studies are necessary to determine the efficacy of chemoprophylaxis and to develop evidence-based clinical practice guidelines to minimize VTE after ACL reconstruction.

Variability of acetabular coverage between supine and weightbearing pelvic radiographs.

BACKGROUND: Radiographic measures of acetabular coverage are essential screening tools used to characterize bony structure contributing to femoroacetabular impingement (FAI). Small changes in pelvic tilt result in altered radiographic measures of acetabular coverage. Positional changes in pelvic tilt are known to occur between the supine and weightbearing positions. It is unclear whether alteration of pelvic tilt between these positions is clinically sufficient to influence measures of acetabular coverage. PURPOSE/HYPOTHESIS: To determine whether, and to what degree, imaging position (supine vs weightbearing) is capable of altering several measures of acetabular orientation: pubic symphysis to sacrococcygeal distance (PSSC), angle of Sharp (SA), Tönnis angle (TA), percentage of acetabular crossover (CO), and lateral center-edge angle of Wiberg (LCEA). The hypothesis was that imaging position would significantly alter all measures of acetabular orientation. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 2. METHODS: A total of 50 consecutive symptomatic hips referred to a single provider for FAI were evaluated with standardized supine and weightbearing anteroposterior pelvic radiographs. Two independent reviewers blinded to patient positioning reviewed each radiograph at 2 separate time points. Mean measurements in each position were compared by use of paired Student t tests, and a Bonferroni-adjusted significance level of P = .01 was used to represent significance. RESULTS: Statistically significant differences between the supine and weightbearing radiographs were identified for PSSC and all measures of acetabular coverage (P < .003). The mean PSSC decreased between the supine and weightbearing positions by an average of 13.4 mm (P < .001), thereby resulting in decreased mean LCEA, TA, SA, and CO of 1.2°, 1.3°, 0.8°, and 6.3%, respectively (P < .002). The change in positional pelvic tilt was not uniformly predictable and accounted for large measurement changes in some individuals. PSSC also demonstrated considerable inter- and intrasubject variability but averaged 55.8 mm supine and 44.9 mm weightbearing for females and 37.0 mm supine and 20.6 mm weightbearing for males. CONCLUSION: In this study of nonarthritic adult patients with hip pain, the data indicate that positional changes are capable of significantly altering pelvic tilt and radiographic measures of acetabular coverage. It appears that the weightbearing position typically, but not universally, correlates with additional posterior pelvic tilt and decreased measures of acetabular coverage. Individual positional variability can contribute to large-magnitude changes in radiographic acetabular measures.

The effect of pelvic tilt on radiographic markers of acetabular coverage.

BACKGROUND: Radiographic indices of acetabular coverage are crucial to objectively characterize femoroacetabular impingement and plan bony decompression. It is established that changes in pelvic inclination result in alterations of acetabular crossover; however, it is unclear what influence this has on other measures of acetabular anatomy. HYPOTHESIS: The objective of the present study was to determine if, and to what degree, a variation in pelvic tilt alters 4 measures of acetabular anatomy: the angle of Sharp, Tönnis angle, percentage of acetabular crossover, and lateral center edge angle (LCEA). The hypothesis was that pelvic tilt would significantly alter all measures of acetabular coverage. STUDY DESIGN: Descriptive laboratory study. METHODS: Fluoroscopic images of 8 adult hemipelvises were obtained at 7 positions of rotation in the sagittal plane to investigate the change of each measurement in response to pelvic orientation. Two reviewers obtained measurements from each image at 2 separate time points. RESULTS: Each increment of pelvic inclination resulted in increased measures of acetabular coverage for all measurements, whereas each increment of decreased pelvic inclination resulted in decreased measures of acetabular coverage for all measurements. Significant differences in the measured LCEA, acetabular crossover, and Tönnis angle were identified at each increment of tilt as compared with neutral radiographs. No significant differences could be identified for the angle of Sharp. CONCLUSION: Pelvic tilt significantly alters the measures of LCEA, crossover, and Tönnis angle in this cadaveric study. Pelvic inclination results in increased measures of acetabular coverage, whereas decreasing inclination decreases each measure. CLINICAL RELEVANCE: Given the known individual and positional pelvic tilt variability, standing anteroposterior pelvic radiographs may provide a more physiological representation of acetabular coverage in the young adult population.