The Femoral Head "Divot" Sign: A Useful Arthroscopic Sign of Hip Microinstability

The Windshield Wiper Sign Is an Instability-Related Osteochondral Defect of the Anterolateral Femoral Head

PURPOSE

To investigate a radiographic sign believed to be indicative of hip instability and acetabular suction seal disruption in the native hip, coined the "windshield wiper" (WSW) sign.

METHODS

A retrospective review was performed for patients who underwent periacetabular osteotomy (PAO) with the senior author between March 2021 and September 2023. A WSW sign was identified on plain films as a concave or flat osteochondral defect on the anterolateral femoral head extending medial to the head-neck junction with resultant loss of femoral head sphericity in the native hip. Every patient underwent a standardized series of radiographs, as well as computed tomography and magnetic resonance imaging. All patients underwent arthroscopy before PAO to address intra-articular pathology and other indicated procedures. The osteochondral defect and resultant suction seal disruption were verified during arthroscopy. These patients were then compared with a control group of arthroscopically treated hips without hip instability.

RESULTS

Of 250 patients reviewed, a total of 19 hips in 17 patients (prevalence of 7.6%) demonstrated radiographic evidence of the WSW sign. All patients with a WSW sign presented with symptomatic clinical hip instability requiring a PAO. The mean patient age was 31.2 years, with a mean lateral center-edge angle (LCEA) of 14.3°. There were 13 hips (68.4%) with dysplasia, 4 (21.1%) with borderline dysplasia, and 2 (10.5%) with a normal LCEA. All patients with a WSW sign and LCEA ≥ 20° displayed significant femoral antetorsion abnormalities. All arthroscopic videos and images demonstrated a compromised suction seal. Of the 50 control group hips reviewed, the WSW sign was not identified.

CONCLUSIONS

The WSW sign is an uncommon radiographic finding in patients with hip instability. When identified, it can be predictive of substantial instability, especially in cases which are otherwise considered borderline dysplasia or normal based on LCEA.

LEVEL OF EVIDENCE

Level III, retrospective comparative case control study.

Can Hip Passive Range of Motion Predict Hip Microinstability? A Comparative Study

Background

Hip microinstability is an increasingly recognized cause of pain and disability in young adults. It is unknown whether differences in passive hip range of motion (ROM) exist between patients with versus without hip microinstability.

Hypothesis

Underlying ligamentous and capsular laxity will result in differences in clinically detectable passive ROM between patients with femoroacetabular impingement (FAI), patients with microinstability, and asymptomatic controls.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

A retrospective review of all patients undergoing hip arthroscopy between 2012 and 2018 was conducted. Patients with a diagnosis of isolated microinstability based on intraoperative findings were identified and classified as having isolated FAI, instability, or FAI + instability. Patients without a history of hip injury were included as controls. Range of motion was recorded in the supine position for flexion, internal rotation, and external rotation. Univariate and multivariate analysis was performed on each measurement in isolation as well as combinations of motion to include total rotation arc, flexion + rotation arc, and flexion + 2× rotation arc Models were then created and tested to predict instability status.

Results

In total, 263 hips were included: 69 with isolated instability, 50 with FAI, 50 with FAI + instability, and 94 control hips. A higher proportion of patients in the instability and FAI + instability groups were female compared with the FAI and control groups (P < .001). On univariate analysis, differences were found in all groups in all planes of motion (P < .001). Multivariable analysis demonstrated differences in all groups in flexion and flexion + rotation arc. In symptomatic patients, the best performing predictive model for hip microinstability was flexion + rotation arc ≥200° (Akaike information criterion, 132.3; P < .001) with a sensitivity of 68.9%, specificity of 80.0%, positive predictive value of 89.1%, and negative predictive value of 51.9%.

Conclusion

Patients with hip microinstability had significantly greater ROM than symptomatic and asymptomatic cohorts without hip microinstability. Symptomatic patients with hip flexion + rotation arc ≥200° were highly likely to have positive intraoperative findings for hip microinstability, whereas instability status was difficult to predict in patients with a flexion + rotation arc of <200°.

The diagnosis of hip microinstability is correlated with ease of intra-operative hip distraction

PURPOSE

Hip microinstability has emerged as a contributor to young adult, non-arthritic hip pain. There is a paucity of objective clinical data to identify patients with hip microinstability and guide surgical treatment. The purpose of this study was to identify the degree of distractibility in patients with and without microinstability undergoing hip arthroscopy.

METHODS

A single-surgeon series of hip arthroscopies were retrospectively reviewed from 2014-2020. All procedures were performed with paralysis on a fracture table with a perineal post where 1 turn of fine traction equates to 4 mm of axial traction. Diagnosis was recorded as isolated instability, instability plus femoroacetabular impingement (FAI), and isolated FAI. Operative reports were reviewed to collect patient demographic data, number of turns of traction required for adequate distraction of the femoral head relative to the acetabulum (10 mm), and the presence of residual subluxation after initial traction was released.

RESULTS

A total of 464 patients were identified, 26 (5.6%) with isolated microinstability, 183 (39.4%) with microinstability with FAI anatomy, and 255 (55.0%) with FAI. The concurrent diagnosis of microinstability was associated with decreased turns required to adequately distract the hip. Isolated microinstability patients required 6.9 turns (IQR 4.6-8.8) while those with instability plus FAI required 8.8 turns (IQR 6.5-11) and isolated FAI required 19.1 turns (IQR 15-22). Residual subluxation after removal of negative intra-articular pressure but before performing the hip arthroscopy was more commonly associated with instability, occurring in 84.6% of isolated instability and 86.9% of instability plus FAI as compared with 29.8% in the isolated FAI cohort.

CONCLUSION

A diagnosis of hip microinstability, with or without features of FAI, is associated with decreased axial traction required to distract the hip. These data support the use of intra-operative ease of distraction as a method of identifying patients with hip microinstability.

LEVEL OF EVIDENCE

Level III.

Update on contribution of hip labral tears to hip pain: A narrative review

Hip labral tears are found in 22-55% of individuals with hip pain, but labral tears without cysts are usually not responsible for hip pain, which originates mostly from other structures than the torn labrum, like osteochondral, but also tendinous injuries (rectus femoris, gluteus minimus, iliopsoas) or capsulo-ligamentous tears (iliofemoral ligaments, ligament teres). Those lesions are mainly the consequences of underlying unrecognized functional acetabular dysplasia, and/or femoroacetabular impingements. Although the early repair of labral tears in young sportsmen induces a marked and lasting relief, and might delay the onset of osteoarthritis, the microinstability fostered by labral damages seems less important than underlying dysplasias/impingements. This narrative review details recent findings on: (i) the various mechanisms of pain associated with labral tears; (ii) few evidence for hip microinstability induced by isolated labral tears; (iii) how to best detect labral tears, both clinically (including through IROP test) and on imaging (MRI, MRA, computed tomography arthrography, ultrasound). Some authors suggested to use pull-out tests during surgery, but pulling of hips do not seem to increase much diagnostic performances of ultrasounds. Ultrasound-guided intra-articular and peri-articular injections may tell how often hip pain is exclusively induced by peri-capsular injuries secondary to the acetabular dysplasia/femoro-acetabular impingements already responsible for labral tears. Further works could tell whether labral repair, tendinous debridement, plication of capsule, and/or focal denervation, may induce lasting reliefs of pain induced by the chronic contraction of surrounding muscles (rectus femoris, gluteus minimus, psoas), whose deep aponeuroses mix with the superficial fibres of the thick hip capsule.

Criteria for the Operating Room Confirmation of the Diagnosis of Hip Instability: The Results of an International Expert Consensus Conference

PURPOSE

The purpose of this study was to establish an international expert consensus on operating room findings that aid in the diagnosis of hip instability.

METHODS

An expert panel was convened to build an international consensus on the operating room diagnosis/confirmation of hip instability. Seventeen surgeons who have published or lectured nationally or internationally on the topic of hip instability were invited to participate. Fifteen panel members completed a pre-meeting questionnaire and agreed to participate in a 1-day consensus meeting on May 15, 2021. A review of the literature was performed to identify published intraoperative reference criteria used in the diagnosis of hip instability. Studies were included for discussion if they reported and intraoperative findings associated with hip instability. The evidence for and against each criteria was discussed, followed by an anonymous voting process. For consensus, defined a priori, items were included in the final criteria set if at least 80% of experts agreed.

RESULTS

A review of the published literature identified 11 operating room criteria that have been used to facilitate the diagnosis of hip instability. Six additional criteria were proposed by panel members as part of the pre-meeting questionnaire. Consensus agreement was achieved for 8 criteria, namely ease of hip distraction under anesthesia (100.0% agreement), inside-out pattern of chondral damage (100.0% agreement), location of chondral damage on the acetabulum (93.3% agreement), pattern of labral damage (93.3% agreement), anteroinferior labrum chondral damage (86.7% agreement), perifoveal cartilage damage (97.6% agreement), a capsular defect (86.7% agreement), and capsular status (80.0% agreement). Consensus was not achieved for 9 items, namely ligamentum teres tear (66.7% agreement), arthroscopic stability tests (46.7% agreement), persistent distraction after removal of traction (46.7% agreement), findings of examination under anesthesia (46.7% agreement), the femoral head divot sign (40.0% agreement), inferomedial synovitis (26.7% agreement), drive-through sign (26.7% agreement), iliopsoas irritation (26.7% agreement) and ligamentum teres-labral kissing lesion (13.3% agreement). All experts agreed on the final list of 8 criteria items reaching consensus.

CONCLUSION

This expert panel identified 8 criteria that can be used in the operating room to help confirm the diagnosis of hip instability.

LEVEL OF EVIDENCE

Level V expert opinion.

Female gender, decreased lateral center edge angle and a positive hyperextension-external rotation test are associated with ease of hip distractability at time of hip arthroscopy

PURPOSE

To identify factors associated with ease of hip distraction at the time of hip arthroscopy.

METHODS

A retrospective review of patients 17-50 years old undergoing hip arthroscopy with a single high-volume hip arthroscopist was performed from 2014 to 2020. Demographics, clinical history, examination, and imaging findings were collected. Distractibility was quantified using turns of fine traction (1 turn = 4 mm axial distraction) with the patient paralyzed on a fracture table with a well-padded perineal post Fine axial traction was applied after the patient's perineum contacted the post. Demographic and clinical predictors of ease of distractibility were analyzed with simple linear regression models. Significant predictors were subsequently added to a multivariable linear regression model, estimating the effect of each variable.

RESULTS

In total, 453 patients were included, with an average age of 31.6 years (± 9.2) and 45.9% females. In univariate analysis, gender, race, BMI, range of motion, hyperextension-external rotation (HEER) test, the abduction-extension-external rotation test, and lateral center edge angle (LCEA) were associated with the number of fine traction turns required to distract the hip. On multivariable analysis, lower LCEA (p = 0.002), female gender (p < 0.001), and a positive HEER test (p = 0.045) were associated with decreased turns required for adequate hip distraction.

CONCLUSION

Female gender, decreased LCEA, and a positive HEER test are associated with decreased axial traction required for adequate hip distraction at the time of hip arthroscopy. As ease of distractibility has been associated with hip microinstability, these findings may allow pre-operative identification of hip instability patients and aid in pre-operative counseling, risk stratification and capsular management planning.

LEVEL OF EVIDENCE

IV.

CLINICAL RELEVANCE

Preoperative identification of risk factors for ease of hip distraction may raise pre-surgical suspicion and, when coupled with other intraoperative findings, may aid in the diagnosis and management of hip microinstability.

Pre- and intraoperative decision-making challenges in hip arthroscopy for femoroacetabular impingement

There has been a marked increase in the number of hip arthroscopies performed over the past 16 years, primarily in the management of femoroacetabular impingement (FAI). Insights into the pathoanatomy of FAI, and high-level evidence supporting the clinical effectiveness of arthroscopy in the management of FAI, have fuelled this trend. Arthroscopic management of labral tears with repair may have superior results compared with debridement, and there is now emerging evidence to support reconstructive options where repair is not possible. In situations where an interportal capsulotomy is performed to facilitate access, data now support closure of the capsule in selective cases where there is an increased risk of postoperative instability. Preoperative planning is an integral component of bony corrective surgery in FAI, and this has evolved to include computer-planned resection. However, the benefit of this remains controversial. Hip instability is now widely accepted, and diagnostic criteria and treatment are becoming increasingly refined. Instability can also be present with FAI or develop as a result of FAI treatment. In this annotation, we outline major current controversies relating to decision-making in hip arthroscopy for FAI. Cite this article: Bone Joint J 2022;104-B(5):532-540.

Central Femoral Head Chondromalacia Is Associated with a Diagnosis of Hip Instability

Purpose

To compare the locations and patterns of femoral head chondral damage in patients with instability in contrast to those with femoroacetabular impingement (FAI) without instability.

Methods

All consecutive hip arthroscopies were reviewed from 2013 to 2020 from a single surgeon. Intraoperative records were reviewed on all patients identified to have femoral head chondromalacia. Data were collected to include laterality, location of femoral head chondromalacia, intraoperative diagnosis (instability and/or FAI subtype), and ease of distractibility. The location of the femoral head chondromalacia was defined on the basis of intraoperative description. Chi-squared and Fisher’s exact tests were used for categorical variables, and a two-sample t test was used for continuous variables. Statistical significance was set at P < .05.

Results

A total of 64 patients were in the study cohort, with 32 patients identified as having non-central head chondromalacia and 32 patients identified as having central head chondromalacia. Of the patients with central head chondromalacia, 81% were diagnosed with instability. Central head chondromalacia was associated with a sensitivity of 84% (71%-97%), specificity of 82% (69%-95%), and positive predictive value of 81% (67%-95%).

Conclusions

A high percentage of patients with central femoral head chondromalacia were found to have hip microinstability. These results suggest that there is a pattern of femoral head chondral damage in patients with hip microinstability.

Level of Evidence

Level III, case-control study.