Cam Osteochondroplasty for Femoroacetabular Impingement Increases Microinstability in Deep Flexion: A Cadaveric Study

The Contribution of Soft Tissue and Bony Stabilizers to the Hip Suction Seal: A Systematic Review of Biomechanical Studies

BACKGROUND

Previous biomechanical studies have identified capsular closure, labral repair or reconstruction, and osteochondroplasty as important surgical interventions to improve hip stability.

PURPOSE

To investigate the outcome metrics used to quantify hip stability and assess and measure the relative contributions of the labrum, capsule, and bone to hip stability through a quantitative analysis.

STUDY DESIGN

Systematic review and meta-analysis; Level of evidence, 4.

METHODS

PubMed and Embase databases were searched using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Included studies evaluated cadaveric hip biomechanics related to capsular, labral, and bony management during hip arthroscopy. Studies were assessed for distraction force and distance, fluid measures, and contact forces used to quantify the suction seal. Exclusion criteria included open surgery, arthroplasty, reorientation osteotomy, or traumatic dislocation.

RESULTS

A total of 33 biomechanical studies comprising 322 hips that evaluated 1 or more of the following were included: distraction force or distance (24 studies), fluid measures (10 studies), and contact forces (6 studies). Compared with a capsulotomy or capsulectomy, capsular repair or reconstruction demonstrated greater resistance to distraction (standardized mean difference [SMD], 1.13; 95% CI, 0.46-1.80; P = .0009). Compared with a labral tear, a labral repair or reconstruction demonstrated less resistance to distraction (SMD, -0.67; 95% CI, -1.25 to -0.09; P = .02). Compared with a labral debridement, repair or reconstruction demonstrated greater resistance to distraction (SMD, 1.74; 95% CI, 1.23 to 2.26; P < .00001). No quantitative analysis was feasible from studies evaluating the effect of osseous resection due to the heterogeneity in methodology and outcome metrics assessed.

CONCLUSION

Most biomechanical evidence supports capsulotomy repair or reconstruction to improve hip distractive stability at the end of hip arthroscopic surgery. While the repair of a torn labrum does not improve distractive resistance, it is superior to labral debridement in most biomechanical studies.

Borderline Hip Dysplasia Is Not Associated With Significant Differences in Hip Survivorship or Patient-Reported Outcomes Following Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Propensity-Matched Cohort Study

PURPOSE

To compare hip survivorship and patient-reported outcomes after primary hip arthroscopy for femoroacetabular impingement syndrome (FAIS) in patients with versus without comorbid borderline hip dysplasia (BHD) at 2-year follow-up.

METHODS

A retrospective matched-cohort study was conducted involving patients who underwent primary hip arthroscopy for FAIS with a single surgeon from 2010 to 2019. BHD was defined as lateral center edge angle (LCEA) of 20 to 25°. Subjects with BHD were matched 1:2 to controls without BHD on age, sex, body mass index, and preoperative modified Harris Hip Score (mHHS). Alpha angle, LCEA, Tönnis angle, and acetabular retroversion signs were measured on preoperative and/or postoperative hip radiographs. Patient-reported outcomes were assessed using the mHHS and the Non-Arthritic Hip Score. Hip survivorship, outcome scores, and achievement of the minimum clinically important difference were compared between groups using the Mann-Whitney U test or Fisher exact test, as appropriate. P values <.05 were considered significant.

RESULTS

Thirty-one BHD subjects (mean age 36.8 years, 71.0% female) and 62 controls (mean age 38.0 years, 71.0% female) were included. There were no significant intergroup differences in demographics or preoperative radiographic measurements besides LCEA and Tönnis angle (all P > .05). Intraoperatively, subjects with BHD were found to have significantly shorter labral tears (mean 2.6 vs 2.8 clock-face hours, P = .048), but there were no significant intergroup differences in acetabular or femoral cartilage status (all P > .05). Postoperatively, there were no significant intergroup differences in rates of revision arthroscopy (BHD 6.5% vs control 11.3%) or conversion to total hip arthroplasty (BHD 9.7% vs control 1.6%), in 2-year improvement of the mHHS and Non-Arthritic Hip Score, or in minimum clinically important difference achievement rates (all P > .05).

CONCLUSIONS

BHD is not associated with a significant difference in hip survivorship or patient-reported outcomes following primary hip arthroscopy for FAIS.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Early Postoperative Activities of Daily Living Do Not Adversely Affect Joint Torques or Translation Regardless of Capsular Condition: A Cadaveric Study

PURPOSE

To evaluate the impact of capsular management on joint constraint and femoral head translations during simulated activities of daily living (ADL).

METHODS

Using 6 (n = 6) cadaveric hip specimens, the effect of capsulotomies and repair was then evaluated during simulated ADL. Joint forces and rotational kinematics associated with gait and sitting, adopted from telemeterized implant studies, were applied to the hip using a 6-degrees of freedom (DOF) joint motion simulator. Testing occurred after creation of portals, interportal capsulotomy (IPC), IPC repair, T-capsulotomy (T-Cap), partial T-Cap repair, and full T-Cap repair. The anterior-posterior (AP), medial-lateral (ML), and axial compression DOFs were operated in force control, whereas flexion-extension, adduction-abduction, and internal-external rotation were manipulated in displacement control. Resulting femoral head translations and joint reaction torques were recorded and evaluated. Subsequently, the mean-centered range of femoral head displacements and peak signed joint restraint torques were calculated and compared.

RESULTS

During simulated gait and sitting, the mean range of AP femoral head displacements with respect to intact exceeded 1% of the femoral head diameter after creating portals, T-Caps, and partial T-Cap repair (Wilcoxon signed rank P < .05); the mean ranges of ML displacements did not. Deviations in femoral head kinematics varied by capsule stage but were never very large. No consistent trends with respect to alterations in peak joint restrain torques were observed.

CONCLUSIONS

In this cadaveric biomechanical study, capsulotomy and repair minimally affected resultant femoral head translation and joint torques during simulated ADLs.

CLINICAL RELEVANCE

The tested ADLs appear safe to perform after surgery, regardless of capsular status, because adverse kinematics were not observed. However, further study is required to determine the importance of capsular repair beyond time-zero biomechanics and the resultant effect on patient-reported outcomes.

Hip joint contact pressure and force: a scoping review of in vivo and cadaver studies

Aims

Research on hip biomechanics has analyzed femoroacetabular contact pressures and forces in distinct hip conditions, with different procedures, and used diverse loading and testing conditions. The aim of this scoping review was to identify and summarize the available evidence in the literature for hip contact pressures and force in cadaver and in vivo studies, and how joint loading, labral status, and femoral and acetabular morphology can affect these biomechanical parameters.

Methods

We used the PRISMA extension for scoping reviews for this literature search in three databases. After screening, 16 studies were included for the final analysis.

Results

The studies assessed different hip conditions like labrum status, the biomechanical effect of the cam, femoral version, acetabular coverage, and the effect of rim trimming. The testing and loading conditions were also quite diverse, and this disparity limits direct comparisons between the different researches. With normal anatomy the mean contact pressures ranged from 1.54 to 4.4 MPa, and the average peak contact pressures ranged from 2 to 9.3 MPa. Labral tear or resection showed an increase in contact pressures that diminished after repair or reconstruction of the labrum. Complete cam resection also decreased the contact pressure, and acetabular rim resection of 6 mm increased the contact pressure at the acetabular base.

Conclusion

To date there is no standardized methodology to access hip contact biomechanics in hip arthroscopy, or with the preservation of the periarticular soft-tissues. A tendency towards improved biomechanics (lower contact pressures) was seen with labral repair and reconstruction techniques as well as with cam correction.

Editorial Commentary: Cam Femoroacetabular Impingement Requires Dynamic Assessment of Beta-Angle (Femoroacetabular Excursion Angle) and Consideration of Femoral and Acetabular Version: Cam Impingement in Patients With Acetabular or Femoral Retroversion May Warrant Greater Osteoplasty

Radiographs, magnetic resonance imaging, and computed tomography scans have been commonly used to evaluate femoroacetabular impingement (FAI) and are well accepted forms of surgical planning. Assessing and addressing both the femoral and acetabular sides result in a combination of "one-sided" treatments that, in sum, net a successful treatment of FAI. However, combining one-sided approaches may not consider the dynamic interaction of the femoral head with the acetabulum. Elevated alpha angles alone can be indicative of a cam-type lesion without necessitating the presence of functional FAI. The presence of a cam-type lesion on lateral radiographs, as suggested by a positive alpha angle, does not necessitate a decrease in clearance between the femoral head and acetabular rim as measured by the beta angle. Assessment of the beta angle, or femoroacetabular excursion angle, has the potential to address dynamic nature of FAI more accurately by directly measuring the degree of clearance between the femoral head and acetabulum. In addition, a comprehensive assessment of physical examination findings, particularly range of motion, as well as a summation of acetabular and femoral version (as measured by the McKibbin Index), are required. Cam-type of FAI poses a larger challenge in the patient with acetabular or femoral retroversion, which may warrant greater and more localized osteoplasty, distally, during hip arthroscopy.

The revision hip arthroscopy complex: capsular deficiency, labral deficiency, femoral over-resection and adhesions can result in good survivorship with revision hip arthroscopy

To evaluate the patient-reported outcomes (PROs) and survivorship of combined arthroscopic hip labral reconstruction/augmentation, capsular reconstruction, femoral neck remplissage and lysis of adhesions. Patients ≥18 years old who underwent this combination of procedures during revision hip arthroscopy and were eligible for minimum 2-year follow-up were identified. PRO scores including Hip Outcome Score (HOS)-Activities of Daily Living scale, HOS-Sports scale, modified Harris Hip Score, Short Form 12, and Western Ontario & McMaster Universities Osteoarthritis Index, patient satisfaction and failure rates were analyzed. Seven patients (5 females and 2 males) with average age of 45.0 ± 5.2 (range: 40-54 years) met inclusion criteria. Patients had a median of 1 (range: 1-3) prior hip surgery at an outside institution. All patients had previously undergone femoral osteoplasty, and 85% (6/7) of patients had a labral repair performed. Four patients had no capsule closure performed in their prior procedures. Six patients were available for minimum 2-year follow-up. Two patients converted to total hip arthroplasty: one patient with four prior hip arthroscopies and the other had advanced osteoarthritis with outerbridge grade 3/4 defects requiring microfracture. Mean patient satisfaction was 7 (range: 2-9). At mean follow-up of 3 years, most patients who underwent the combination of labral reconstruction, capsular reconstruction, femoral neck remplissage and lysis of adhesions during revision hip arthroscopy demonstrated improved PROs. This salvage procedure has the potential to restore hip function in patients who have failed an initial hip arthroscopy procedure. In patients with these pathologies present and concomitant joint space narrowing, a total hip arthroplasty may be a more appropriate salvage option.

Arthroscopy Honors Award-Winning Articles and Authors: Our Annual Research Awards

With genuine gratitude to the AANA Education Foundation for their unstinting support, it is our honor to announce Arthroscopy's Annual Awards for the best Clinical Research, Basic Science Research, Resident/Fellow Research, and Systematic Reviews published in 2022, as well as the Most Downloaded and Most Cited papers published 5 years ago. And as is customary in January, our editors update their disclosures of potential conflicts of interest, as we require of authors, and we update our masthead to introduce new members of our Editorial Board and Social Media Board.

Diagnosing Hip Microinstability: an international consensus study using the Delphi methodology

PURPOSE

Hip microinstability is a relatively new diagnosis which is increasingly being discussed in the literature and yet there are no clear guidelines for making a diagnosis. Microinstability has generally been defined as persistent excessive hip motion that has become symptomatic especially with pain. This aim of this Delphi study was to seek expert opinion to formulate a diagnostic criteria for hip microinstability.

METHODS

A Delphi methodology was used for this consensus study. A literature search was conducted on PubMed up to March 2019 using the keywords ((hip) and (microinstability)) to identify relevant articles on this topic. All relevant criteria used for diagnosing hip microinstability were collated to create a questionnaire and further criterion suggested by the experts were included as well. Four rounds of questionnaires were delivered via an online survey platform. Between each round the authors acted as administrating intermediaries, providing the experts with a summary of results and synthesising the next questionnaire. The expert panel was comprised of 27 members: 24 (89%) orthopaedic surgeons and 3 (11%) physiotherapists from around the world.

RESULTS

Expert panel participation in rounds 1-4 was: 27 (100%), 20 (74%), 21 (78%) and 26 (96%) respectively. A literature review by the authors identified 32 diagnostic criteria to populate the first questionnaire. Experts suggested amending three criteria and creating five new criteria. The panel converged on ranking 3 (8%) of criteria as "Not important", 20 (54%) as "Minor Factors" and 14 (38%) as "Major Factors". No criteria was ranked as "Essential". Criteria were subcategorised into patient history, examination and imaging. Experts voted for a minimum requirement of four criteria in each subcategory, including at least six "Major factors". The final diagnostic tool was approved by 20 (77%) of the final round panel.

CONCLUSION

This study describes the first known expert consensus on diagnosing hip microinstability. The relative complexity of the final diagnostic tool is illustrative of the difficulty clinicians' face when making this diagnosis.

LEVEL OF EVIDENCE

V.

Cadaveric Biomechanical Evaluation of Capsular Constraint and Microinstability After Hip Capsulotomy and Repair

Background:

It remains unclear if capsular management contributes to iatrogenic instability (microinstability) after hip arthroscopy.

Purpose:

To evaluate changes in torque, stiffness, and femoral head displacement after capsulotomy and repair in a cadaveric model.

Study Design:

Controlled laboratory study.

Methods:

A biomechanical analysis was performed using 10 cadaveric hip specimens. Each specimen was tested under the following conditions: (1) intact, (2) portals, (3) interportal capsulotomy (IPC), (4) IPC repair, (5) T-capsulotomy (T-cap), (6) partial T-cap repair, and (7) T-cap repair. Each capsular state was tested in neutral (0°) and then 30°, 60°, and 90° of flexion, with forces applied to achieve the displacement-controlled baseline limit of external rotation (ER), internal rotation (IR), abduction, and adduction. The resultant end-range torques and displacement were recorded.

Results:

For ER, capsulotomies significantly reduced torque and stiffness at 0°, 30°, and 60° and reduced stiffness at 90°; capsular repairs failed to restore torque and stiffness at 0°; and IPC repair failed to restore stiffness at 30° (P < .05 for all). For IR, capsulotomies significantly reduced torque and stiffness at 0°, 30°, and 60° and reduced stiffness at 90°; and capsular repairs failed to restore torque or stiffness at 0°, 30°, and 60° and failed to restore stiffness at 90° (P < .05 for all). For abduction, IPC significantly decreased torque at 60° and 90° and decreased stiffness at all positions; T-cap reduced torque and stiffness at all positions; IPC repair failed to restore stiffness at 0° and 90°; and T-cap repair failed at 0°, 60°, and 90° (P < .05 for all). For adduction, IPC significantly reduced torque at 0° and reduced stiffness at 0° and 30°; T-cap reduced torque at 0° and 90° and reduced stiffness at all positions; IPC repair failed to restore stiffness at 0° and 90°; and T-cap repair failed at 0°, 60°, and 90° (P < .05 for all). There were no statistically significant femoral head translations observed in any testing configurations.

Conclusion:

Complete capsular repair did not always restore intact kinematics, most notably at 0° and 30°. Despite this, there were no significant joint translations to corroborate concerns of microinstability.

Clinical Relevance:

Caution should be employed when applying rotational torques in lower levels of flexion (0° and 30°).

Postoperative Alpha Angle Is Predictive of Return to Sport in Athletes Undergoing Hip Arthroscopy for Femoroacetabular Impingement

PURPOSE

To identify clinical and radiographic factors that predict return to sport in athletes undergoing hip arthroscopy and to determine thresholds for significant predictors.

METHODS

Data were reviewed on all patients who underwent primary hip arthroscopy between November 2008 and August 2018. Patients were included if they played professional, college, or high school sports within 1 year before surgery and had preoperative, 3-month, 1-year, and 2-year postoperative patient-reported outcome scores for modified Harris Hip Score, Hip Outcome Score-Sport Specific-Subscale, and Nonarthritic Hip Score. Rates of achieving the minimal clinically important difference also were evaluated. Patients were divided into groups based on whether they returned to sport at the same or greater level. Multivariate logistic regression and receiver operator characteristic analysis were used to evaluate the correlation between significant variables and return to sport.

RESULTS

A total of 136 patients with a mean age of 20.8 ± 7.07 years were included. Among athletes who attempted to return, professional and collegiate athletes returned to sport at any level at a rate of 85.0% (51/60), and high-school athletes returned at a rate of 88.1% (52/59). Competition level, postoperative alpha angle, change in alpha angle, and postoperative patient-reported outcomes were significantly different between groups. Athletes who returned to sport achieved the minimal clinically important difference for Hip Outcome Score-Sport Specific-Subscale at significantly higher rates than athletes who did not return to sport (91.6% vs 71.7%, P = .002, S = 8.97). The multivariate logistic regression model identified postoperative alpha angle as a statistically significant predictor of return to sport (P < .001, S > 9.97 [odds ratio 0.85, 95% confidence interval 0.79-0.91]). The receiver operator characteristic curve for postoperative alpha angle demonstrated acceptable discrimination between patients returning to sport and patients not returning to sport with an area under the curve of 0.71 and a threshold value of 46°. Athletes with a postoperative alpha angle ≤46° returned to sport at significantly higher rates than those with a postoperative alpha angle >46° [(P < .001, S > 9.97 [odds ratio 6.3, 95% confidence interval 2.6-15.2]).

CONCLUSIONS

Postoperative alpha angle was identified as a predictor of return to sport in athletes. The odds of returning to sport were 6.3 times greater in athletes with postoperative alpha angles ≤46° compared with athletes with angles >46°.

LEVEL OF EVIDENCE

III, retrospective cohort study.

Arthroscopy Annual Research Awards: Something to Celebrate

With sincere appreciation to the AANA Education Foundation for their generous support, we announce our Annual Awards for the best Clinical Research, Basic Science Research, Resident/Fellow Research, and Systematic Reviews published in 2021, as well as the Most Downloaded and Most Cited papers published 5 years ago. Also, as is customary and as we require of authors, our editors update their annual disclosures of potential conflicts of interest. Finally, we annually update our masthead, thus introducing a new Associate Editor and many new members of the Editorial Board and Social Media Board.

Muscle and Hip Contact Forces in Asymptomatic Men With Cam Morphology During Deep Squat

Cam morphology is defined as an aspherical femoral head-neck junction that causes abnormal contact of the acetabular rim with the anterior hip. Imaging confirmation of the cam morphology, associated with clinical signs and pain in the hip or groin, is characterized as femoroacetabular impingement (FAI) syndrome. Although some individuals with cam morphology do not experience any symptoms, sparse studies have been done on these individuals. Understanding the way asymptomatic individuals generate muscle forces may help us to better explain the progression of the degenerative FAI process and discover better ways in preventing the onset or worsening of symptoms. The purpose of this study was to compare the muscle and hip contact forces of asymptomatic cam morphology (ACM) and FAI syndrome men compared to cam-free healthy controls during a deep squat task. This prospective study compared 39 participants, with 13 in each group (ACM, FAI, and control). Five deep squatting trials were performed at a self-selected pace while joint trajectories and ground reaction forces were recorded. A generic model was scaled for each participant, and inverse kinematics and inverse dynamics calculated joint angles and moments, respectively. Muscle and hip contact forces were estimated using static optimization. All variables were time normalized in percentage by the total squat cycle and both muscle forces and hip contact forces were normalized by body weight. Statistical non-parametric mapping analyses were used to compare the groups. The ACM group showed increased pelvic tilt and hip flexion angles compared to the FAI group during the descent and ascent phases of the squat cycle. Muscle forces were greater in the ACM and control groups, compared to the FAI group for the psoas and semimembranosus muscles. Biceps femoris muscle force was lower in the ACM group compared to the FAI group. The FAI group had lower posterior hip contact force compared to both the control and ACM groups. Muscle contraction strategy was different in the FAI group compared to the ACM and control groups, which caused different muscle force applications during hip extension. These results rebut the concept that mobility restrictions are solely caused by the presence of the cam morphology and propose evidence that symptoms and muscle contraction strategy can be the origin of the mobility restriction in male patients with FAI.

Editorial Commentary: Hip Cam Overresection May Result in Inferior Outcomes: The Goldilocks Paradox of Too Little, Too Much, or Just Right?

Femoroacetabular impingement is a recognized source of hip pain and cause of labral and articular cartilage injury. Persistent femoroacetabular impingement has been recognized as a source of inferior patient-reported outcomes, and attempts to define a "normal" α-angle has resulted in more aggressive resection of cam lesions. An overzealous femoroplasty may result in iatrogenic hip instability. A dynamic intraoperative examination may be the best way to truly recognize this problem, in particular, by visualizing the loss of the suction seal, as the cam resection engages the acetabulum, resulting in subluxation. A soft tissue "remplissage" salvage procedure may offer an option to correct cam overresection and improve patient outcomes during revision arthroscopy, as we continue to search for the "right" amount of cam correction to perform.

Editorial Commentary: Microinstability After Cam Osteochondroplasty Results From Over-Resection-Everything in Moderation

Cam impingement is one of the most common pathologies treated with hip arthroscopy. While it is a common treatment, it can be difficult to achieve the perfect osteochondroplasty, one that neither over- nor under-resects the head-neck junction. Clinical studies and now biomechanical analysis show over-resection of cam lesions can result in inferior clinical outcomes from microinstability.