Use of intraoperative computed tomography scanning in determining the magnitude of arthroscopic osteochondroplasty

Extent of Cam Resection Relative to Epiphyseal Line and Its Association With Clinical Outcomes After Arthroscopic Treatment for Femoroacetabular Syndrome

Background:

Inadequate resection of cam lesions can cause inferior outcomes after hip arthroscopy and result in revision surgery for femoroacetabular impingement syndrome (FAIS).

Purpose:

To evaluate the association between postoperative cam lesions measured using the proximal boundaries of resection area (PBRE) relative to the epiphyseal line and 2-year outcomes after hip arthroscopy.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Included were patients with FAIS who had undergone primary hip arthroscopy between 2016 and 2018. The PBRE was calculated by measuring the linear distance from the PBRE to the epiphyseal line, dividing it by the diameter of the femoral head, and multiplying by 100; PBRE measurements were made at the 12-, 1-, and 2-o’clock positions on postoperative hip computed tomography. Within each clockface position, patients were divided into subgroups depending on whether their postoperative PBRE was greater than a half standard deviation above the mean (adequate resection) or less than or equal to a half standard deviation above the mean (inadequate resection). Patient-reported outcomes (PROs; Hip Outcome Score–Activities of Daily Living [HOS-ADL], International Hip Outcome Tool–Short Form [iHOT-12], modified Harris Hip Score [mHHS], and pain visual analog scale [VAS]) and rates of achieving the minimal clinically important difference (MCID) and patient-acceptable symptomatic state (PASS) were compared among the subgroups.

Results:

Included were 80 pairs of hips at 12 o’clock, 81 pairs of hips at 1 o’clock, and 80 pairs of hips at 2 o’clock. All subgroups demonstrated significant improvements in PRO scores at a minimum 2-year follow-up compared with preoperatively. At the 12-o’clock position, the subgroup with adequate resection had significantly superior HOS-ADL ( P = .004), iHOT-12 ( P < .001), and mHHS ( P < .001) scores and were more likely to achieve the MCID for the iHOT-12 score ( P = .035) and the PASS for the HOS-ADL ( P = .003), iHOT-12 ( P = .007), and mHHS ( P < .001) scores compared with the matched subgroup. There were no significant differences in PRO scores or rates of MCID and PASS for the 1- or 2-o’clock groups.

Conclusion:

The epiphyseal line may be a useful and reproducible landmark measurement for cam-type deformity. Patients considered to have inadequate resection at 12 o’clock had lower outcome scores at a minimum 2-year follow-up.

Improved Functional Outcome Scores Associated with Greater Reduction in Cam Height Using the Femoroacetabular Impingement Resection Arc During Hip Arthroscopy

PURPOSE

We sought to evaluate the association between postoperative cam lesion measured by the femoroacetabular impingement resection (FAIR) arc and show 2-year patient outcomes following hip arthroscopy.

METHODS

A retrospective review of prospectively gathered data from 2013-2017 was performed. All patients who underwent hip arthroscopy for femoroacetabular impingement resection (FAI) with ≥2-year follow-up were included. Cam FAIR arc measurements were made preoperatively and postoperatively on a 45° Dunn view radiograph. The clinical effect of postoperative cam maximal radial distance (MRD) was assessed using the modified Harris Hip Score (mHHS) and Non-Arthritic Hip Score (NAHS). Patients were divided into subgroups based on relationship to the mean and standard deviations for cam MRD. One half standard deviation above the mean was found to be 3.15 mm.

RESULTS

Sixty-one hips in 59 consecutive patients (age 38.1 ± 13.1; body mass index [BMI]: 25.5 ± 4.3; 36 females) were included. Mean preoperative and postoperative cam maximal radial distances (MRD) were 4.5 ± 1.7 mm and 2.3 ± 1.7 mm (P < .001), respectively. The interclass correlation coefficient was excellent (>.9) for all measurements. There were no differences in age, sex, BMI or preoperative mHHS/NAHS between <3.15 mm and >3.15 mm cam MRD groups (P > .05). Using linear regression, cam MRD was found to be significantly associated with 2-year outcomes for both mHHS (R² = .21, P < .001) and NAHS (R² = .004). Subgroup analysis demonstrated that patients in the cam MRD < 3.15 mm group had significantly higher mHHS (89.7 vs 70.0, P < .001) and NAHS scores (90.5 vs 72.9, P < .001) than those in the >3.15 mm group. Additionally, more patients in the <3.15 mm group reached the minimal clinically important difference (95.2% vs 78.9%, P = .048) and were above patient acceptable symptomatic state (95.2% vs 52.6%, P < .001) compared to the >3.15 mm group.

CONCLUSION

Patients with a lower postoperative cam MRD relative to the FAIR arc demonstrated significantly improved outcomes as compared to those with higher postoperative MRD at two-year follow-up.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

The Femoroacetabular Impingement Resection (FAIR) Arc: An Intraoperative Aid for Assessing Bony Resection During Hip Arthroscopy

Symptomatic femoroacetabular impingement is one of the most common hip pathologies in young athletes. Intraoperative fluoroscopy is commonly used during hip arthroscopy to aid with portal placement and resection of the cam and pincer lesions. However, there are currently no universally agreed-on tools to allow for the assessment of adequacy of femoral and acetabular osteoplasty. Despite the general lack of consensus among hip arthroscopists, the senior author recommends using the femoroacetabular impingement resection arc to guide the adequacy of cam and pincer resection in hip arthroscopy. Using intraoperative fluoroscopy, one should aim to create a continuous "Shenton's line"-type arc along the inferior aspect of the anterior-inferior iliac spine and superolateral femoral neck base by resecting any bone that causes a break in the continuity of this arc.

Mirror Image Modeling of Acetabular Rim Thickness Differences in Patients With Unilateral Femoroacetabular Impingement Syndrome

Purpose

To use mirror imaging to identify the location and magnitude of difference in acetabular rim morphology between the symptomatic and unaffected acetabula in patients with symptomatic unilateral pincer-type or mixed femoroacetabular impingement syndrome (FAIS) using 1-dimensional models created with computed tomography (CT).

Methods

CT scans of bilateral hips in 33 patients diagnosed with unilateral pincer-type or mixed FAIS were obtained. Three-dimensional bilateral hip models were constructed, and the unaffected hemipelvis was superimposed onto the symptomatic side to compare acetabular thickness. Protrusion of the symptomatic side was recorded, and rim morphology was divided into clock face quadrants to analyze the location of greatest magnitude of difference between affected and unaffected acetabula. Analysis of the quadrants was performed using analysis of variance with post hoc Bonferroni correction.

Results

The study group consisted of more females (51.6%) than males, with an average age of 35.72 ± 7.8 years and an average body mass index of 24.3 ± 4.1 kg/m². Of the 33 hips included, 14 were isolated pincer-type FAIS and 19 were mixed. The average preoperative symptomatic side lateral center edge angle was 37.5° ± 7.2° compared with 29° ± 5.1° on the asymptomatic side (P = .001). The symptomatic acetabular rim was on average 0.43 ± 0.18 mm thicker than the corresponding location on the unaffected rim. When the acetabulum was divided into clock face quadrants, the 12 to 3 o'clock position showed the greatest difference between symptomatic and unaffected sides (0.55 ± 0.18 mm) compared with the 3 to 6 o'clock position (0.4 ± 0.28 mm; P = .006), 6 to 9 o'clock (0.34 ± 0.07 mm; P < .001), and 9 to 12 o'clock (0.38 ± 0.03; P = .001).

Conclusions

Patients with unilateral, symptomatic pincer-type or mixed FAIS show statistical differences in rim thickness between the affected and unaffected acetabula. Small changes in acetabular rim morphology on the order of ≤0.5 mm may be the difference between symptomatic FAIS and the unaffected hip.

Level of Evidence

IV, case series.

Application of three dimensional printing in surgery for cam type of femoro-acetabular impingement

Surgical treatment of femoroacetabular impingement (FAI) focuses on improving the clearance for hip motion and alleviation of femoral abutment against the acetabular rim. Cam type of impingement is managed by performing an osteochondroplasty to remove the excess impinging bone from the head neck junction, thus improving the head neck offset. This procedure can be done by safe surgical dislocation, arthroscopy assisted mini-open method or all arthroscopy technique. Whatever be the approach, adequate excision of the Cam deformity is necessary to avoid suboptimal results. Under-excision leads to persistent symptoms and progression of disease, while over-excision can lead to weak bone vulnerable to fracture or disturb the labral seal. Various techniques utilized for intra-operative evaluation of amount of excision required described in literature are fluoroscopy, spherometer gauges, intra-operative Computed Tomography (CT) scan, navigation etc. Rapid prototyping, also called as three dimensional (3D) printing, is a technology to create dimensionally accurate model from a computer-assisted design. Accurate physical models can be designed from the medical imaging data like CT scans and 3D printed to aid in various medical applications. Its application in orthopaedic field is on a rise, recently. However, there is no report on utilization of this technique in surgeries for FAI. We have reported a case of Cam type FAI in an eighteen year old boy, which we treated surgically by performing osteochondroplasty using safe surgical dislocation. We did CT based virtual surgical planning to design femoral head and neck jigs, which were 3D printed and used intra-operatively to guide for adequate and optimum excision of bone at head neck junction. We found these customized jigs accurate and useful for the surgery. However, a comparison study with various other techniques is warranted for a detailed research on its usefulness and challenges. The main purpose of this article is to elaborate on the technical steps for designing of jigs for 3D printing to guide in osteochondroplasty surgery for FAI.

Quantitative evaluation of residual bony impingement lesions after arthroscopic treatment for isolated pincer-type femoroacetabular impingement using three-dimensional CT

PURPOSE

The objective of this study is to determine the clinical characteristics of residual bony impingement lesions after arthroscopic treatment for pincer-type femoroacetabular impingement (FAI); and to determine the effects of residual bony impingement lesions on the clinical outcomes after 2 years of follow-up.

METHODS

From December 2010 to January 2012, 42 patients underwent arthroscopic surgery for symptomatic pincer-type FAI. Clinical outcomes were evaluated using the modified Harris Hip Score (mHHS) and satisfaction scores. To quantitatively evaluate the acetabular bony impingement lesions, the acetabular bony impingement angles were measured on three-dimensional CT scans. The incidence and residual rates of residual bony impingement were calculated. According to residual rates, the patients were divided into three groups: group 1, residual rate <10 %; group 2, residual rate 10-20 %; and group 3, residual rate >20 %.

RESULTS

Thirty patients met the inclusion criteria and were enrolled in this study. The mean age was 34.5 years. The mean follow-up was 26.3 months. Nineteen cases had residual bony impingement lesions after surgery. The incidence was 63.3 % (19/30). Sixteen cases (84.2 %) had residual bony impingement lesions posterior to the actual acetabular resection zones. The preoperative and postoperative bony impingement angles were 77.47° ± 21.31° and 12.94° ± 18.04°, respectively. The residual rate was 14.48 %. The overall mHHS significantly improved (P < 0.001) from 55.18 ± 7.96 preoperatively to 94.71 ± 4.39 postoperatively. The overall satisfaction rate was 76.66 %. The postoperative mHHSs of groups 1-3 were 95.86 ± 1.71, 95.23 ± 1.99, and 85.52 ± 6.41, respectively. Group 3 exhibited significantly lower postoperative mHHS compared to the other two groups (P = 0.001). The satisfaction rates in groups 1-3 were 92.86, 80, and 33.33 %, respectively. The satisfaction rate in group 3 was significantly worse than those of the other two groups (P = 0.017). There was a significant inverse linear relationship between the residual rate of bony impingement lesions and the postoperative mHHS (R (2) = 0.516, P < 0.05).

CONCLUSION

The incidence of residual impingement lesions after arthroscopic pincer-type FAI correction was 63.3 %. The residual rate was 14.48 %. The residual impingement lesions were primarily in the posterior portion of the acetabulum. The clinical outcomes were associated with the residual rate of bony impingement lesions. The patients with residual rates >20 % exhibited significantly lower clinical scores and satisfaction rates.

The effect of acetabular rim recession on anterior acetabular coverage: a cadaveric study using the false-profile radiograph

BACKGROUND

The majority of rim recession for femoroacetabular impingement (FAI) is performed anteriorly and has traditionally been assessed by the lateral center-edge (CE) angle, which correlates most closely with lateral coverage. The radiographic false-profile view permits measurement of anterior coverage via the anterior CE angle and more closely correlates with anterior coverage.

PURPOSE

To answer the following questions: (1) How does incremental anterior rim recession change lateral and anterior CE angles? and (2) Can these changes be predicted by a formula?

STUDY DESIGN

Descriptive laboratory study.

METHODS

Twelve cadaveric hips were dissected free of soft tissue to expose the anterior acetabular rim. Incremental resections of 2.5 mm (range, 0-10 mm) were performed from the 12- to 3-o'clock position using a Dremel rotary tool. Anteroposterior hip and false-profile radiographs were obtained at each interval using a fluoroscopic C-arm. The lateral and anterior CE angles were measured by 3 orthopaedic surgeons.

RESULTS

The average preresection lateral CE angle was 35.1°, and the mean decrease in lateral CE angle from 0 to 10 mm was 9.9°; the average preresection anterior CE angle was 38.4° and the mean decrease in anterior CE angle from 0 to 10 mm was 18.2°. The anterior CE angle decreased by a factor of 1.9 when compared with the lateral CE angle (P = 2 × 10(-7)). The lateral CE angle decreased by approximately 1° (1.0°) per millimeter of rim recessed. The anterior CE angle decreased by approximately 2° (1.8°) per millimeter of rim recessed.

CONCLUSION

The lateral CE angle should not be extrapolated to reflect anterior acetabular coverage. The anterior CE angle is a superior marker and predictably decreases with rim recession at double the rate of the lateral CE angle.

CLINICAL RELEVANCE

The false-profile view is recommended in the perioperative workup for all patients undergoing arthroscopic treatment of pincer impingement.

Do plain radiographs correlate with CT for imaging of cam-type femoroacetabular impingement?

BACKGROUND

Three-dimensional imaging (CT and MRI) is the gold standard for detecting femoral head-neck junction malformations in femoroacetabular impingement, yet plain radiographs are used for initial diagnostic evaluation. It is unclear, however, whether the plain radiographs accurately reflect the findings on three-dimensional imaging.

QUESTIONS/PURPOSES

We therefore: (1) investigated the correlation of alpha angle measurements on plain radiographs and radial reformats of CT scans; (2) determined which radiographic views are most sensitive and specific in detecting head-neck deformities present on CT scans; and (3) determined if specific radiographic views correlated with specific locations on the radial oblique CT scan.

METHODS

We retrospectively reviewed 41 surgical patients with preoperative CT scans (radial oblique reformats) and plain radiographs (AP pelvis, 45° Dunn, frog lateral, and crosstable lateral). Alpha angles were measured on plain radiographs and CT reformats.

RESULTS

The complete radiographic series was 86% to 90% sensitive in detecting abnormal alpha angles on CT. The maximum alpha angle on plain radiographs was greater than that of CT reformats in 61% of cases. Exclusion of the crosstable lateral did not affect the sensitivity (86%-88%). The Dunn view was most sensitive (71%-80%). The frog lateral showed the best specificity (91%-100%). Substantial correlations (intraclass correlation coefficients, 0.64-0.75) between radiograph and radial oblique CT position were observed, including AP/12:00 (superior), Dunn/1:00 (anterolateral), frog/3:00 (anterior), and crosstable/3:00 (anterior).

CONCLUSIONS

For diagnostic and treatment purposes, a three-view radiographic hip series (AP pelvis, 45° Dunn, and frog lateral) effectively characterizes femoral head-neck junction malformations.

LEVEL OF EVIDENCE

Level II, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Preoperative three-dimensional CT predicts intraoperative findings in hip arthroscopy

BACKGROUND

Currently, plain radiographs and MRI are the standard imaging modalities used for diagnosing femoroacetabular impingement (FAI) and preoperative planning for arthroscopic treatment of FAI. The value of three-dimensional (3D) CT for these purposes is unclear.

QUESTIONS/PURPOSES

We therefore determined the reliability of CT assessment of FAI and whether CT findings of hip disease predict arthroscopic findings.

METHODS

We retrospectively assessed the preoperative CT scans of 118 patients who underwent primary hip arthroscopy. Intraoperative findings, including size of the cam lesion, presence of an acetabular labral articular disruption lesion, and one of four types of labral tear were recorded and compared with the retrospectively read CT findings.

RESULTS

Agreement analysis between CT and intraoperative detection of FAI yielded kappa values of 0.48 for cam lesions and 0.16 for pincer lesions. Increasing values for the CT-based alpha angle correlated with increasing severity of arthroscopically assessed acetabular labral articular disruption grade. Each pattern of FAI predicted a specific labral tear type.

CONCLUSIONS

Our data suggest CT has moderate value in predicting mechanically based labral tear patterns, although better parameters for assessment of pincer lesions are needed. Diagnostic assessment of patients with suspected FAI may be improved with use of 3D CT.