Proximal Femoral Deformity Research Articles

The role of altered proximal femoral geometry in impaired pelvis stability and hip control during CP gait: A simulation study

Children with cerebral palsy (CP) often present aberrant hip geometry, more specifically increased femoral anteversion and neck-shaft angle. Furthermore, altered gait patterns are present within this population. This study analyzed the effect of aberrant femoral geometry, as present in subjects with CP, on the ability of muscles to control hip and knee joint kinematics. Given the specific gait deficits observed during crouch gait, increased ability to abduct, externally rotate the hip and extend the knee and hip were denoted as beneficial effects. We ran dynamic simulations of CP and normal gait using two musculoskeletal models, one reflecting normal femoral geometry and one reflecting proximal femoral deformities. The results show that the combination of aberrant bone geometry and CP-specific gait characteristics beneficially increased the ability of gluteus medius and maximus to extend the hip and knee. In contrast, the potentials of the hamstrings to extend the hip decreased whereas the potentials to flex the knee increased. These changes closely followed the observed changes in the muscle moment arm lengths. In conclusion, this study emphasizes the concomitant effect of the presence of proximal femoral deformity and CP gait characteristics on the muscle control of hip and knee joint kinematics during single stance. Not accounting for subject-specific geometry will affect the calculated muscles’ potential during gait. Therefore, the use of generic models to assess muscle function in the presence of femoral deformity and CP gait should be treated with caution.

Discrepancia de longitud de los miembros inferiores tras canalización arterial en niños

ObjectivesThe aim of this study was to assess the relationship between arterial cannulations and the development of limb length discrepancies in childhood or impaired growth of the proximal femur. Material and MethodsA retrospective study was conducted on 300 children who required arterial cannulation and/or cardiac catheterisation during childhood in relation to congenital heart diseases. Seven of these patients were referred from the Paediatric Cardiology clinic due to a limb length discrepancy and/or proximal femoral deformities. ResultsSeven children, with a mean age of 10 years, were referred to our clinic. The mean length discrepancy was 2.7cm, and was more frequent on the right side. Three of the patients presented with proximal femoral deformities: two cases of caput valgum and one of bilateral physeal arrest of the greater trochanter. All children were initially treated with a shoe lift in the shortest limb. One of them required a tibial lengthening and two others are awaiting a similar procedure. ConclusionWe recommend clinical and radiological follow-up of patients who have undergone catheterisation during their infancy due to the relationship between these techniques and the risk of developing a limb length discrepancy.

Determinants of Hip Displacement in Children With Cerebral Palsy.

Coxa valga and femoral anteversion often are seen in patients with spastic hip displacement and osteotomy is recommended. However, the relationship between femoral deformities and hip displacement has not been clearly defined and other factors, such as joint motion and posture, should be considered before recommending treatment. For children with cerebral palsy with Gross Motor Function Classification System Level IV or V, we questioned (1) whether hip abduction range correlates with hip displacement, (2) what the relationships are between proximal femoral deformities and hip displacement, and (3) whether the patient with a windblown posture has greater degrees of femoral anteversion? We retrospectively studied 31 consecutive children with cerebral palsy with Level IV or V gross motor function who underwent three-dimensional CT for preoperative assessment of hip displacement between January 2010 and December 2013. Among the children, 23 had a windblown posture and eight had symmetric hip motion. Femoral anteversion and true neck-shaft angle were measured from the three-dimensional CT images. Migration percentage was the dependent variable we chose to study in relation to femoral anteversion, neck-shaft angle, maximal hip abduction, and hip flexion contracture, using correlations and multiple linear regressions. Using ANOVA and Scheffé's post hoc tests, we analyzed and compared the data of 23 abducted hips and 23 adducted hips in the 23 children with windblown posture and in 16 displaced hips in the eight children with symmetric hip abduction. Greater migration percentage was associated with less hip abduction range (r = -0.86; p < 0.001). Femoral anteversion had a weak correlation (r = 0.28; p < 0.05) to migration percentage, and the association became insignificant after considering hip abduction motion. Adducted windblown hips had greater femoral anteversion than the symmetric displaced hips and abducted windblown hips (46° vs 36° and 38°, respectively; p < 0.05). Our study results did not support a relationship between femoral deformities and hip displacement after considering gross motor function and hip abduction motion. Greater femoral anteversion was noted in the adducted hips of patients with windblown posture, and derotation osteotomy is especially recommended. Level III, diagnostic study.

Osteoarthritis of the hip in fibrous dysplasia of the proximal femur.

Deformity of the proximal femur in fibrous dysplasia leads to deviation of the mechanical axis of the hip, which may lead to the development of secondary osteoarthritis (OA). This study investigated the prevalence and predisposing factors for the development of OA in patients with fibrous dysplasia of the proximal femur. We reviewed the records of 209 patients from our institutional database with fibrous dysplasia of the proximal femur, investigating possible predisposing factors including patient demographics, the extent of the coxa vara deformity, the presence of peri-articular disease, and the overall burden of skeletal disease. Of the 209 patients, 24 (12%) had radiological evidence of OA in the ipsilateral hip. The prevalence was significantly higher in patients with polyostotic fibrous dysplasia compared with those with monostotic disease (p < 0.001). In a subgroup analysis of patients with polyostotic disease, the extent of deformity (quantified using the neck-shaft angle), and the presence of peri-articular disease (whether in the head of the femur or the acetabulum) were significant predictors of osteoarthritis (neck-shaft angle likelihood ratio (LR) = 0.847 per 1° increase, p = 0.004; presence of lesion in the head of the femur LR = 9.947, p = 0.027; presence of lesion in the acetabulum LR = 11.231, p = 0.014). Our data suggest that patients with polyostotic fibrous dysplasia have a high risk of developing secondary OA of the hips. This risk is higher in patients with peri-articular disease, and those with a more severe deformity of proximal femur.

Incidence and predisposing factors of periprosthetic proximal femoral fractures: a literature review.

The purpose of this review article was to investigate the incidence and predisposing factors for periprosthetic proximal femoral fractures (PFF) following total hip arthroplasty. We performed a comprehensive search of the medical literature in MEDLINE and EMBASE databases to review articles related to PFF, their incidence and risk factors. The incidence of PPF after primary THA was, in general, lower than after revision THA both for intra- and postoperative PFF. The rate of intraoperative PFF ranged from 0.1% to 27.8% and of postoperative PFF from 0.07% to 18%. Predisposing factors for intraoperative PFF are osteoporosis, rheumatoid arthritis, femoral preparation and surgical technique used to insert the rasp or femoral component, the use of press-fit cementless stems, and revision THA. In case of postoperative PFF, the following seem to be significant risk factors: advanced age, female gender, post-traumatic osteoarthritis, osteoporosis and rheumatoid arthritis, proximal femoral deformities, previous surgery of the affected hip, implant type (especially cementless stems and press-fit implantation), technical errors such as cortical perforation, cortical stress risers, low-energy trauma, osteolysis, loosening and revision THA.

CORR Insights(®): Modified Dunn Procedure is Superior to In Situ Pinning for Short-term Clinical and Radiographic Improvement in Severe Stable SCFE.

T he surgical treatment for slipped capital femoral epiphysis (SCFE) treatment has evolved in important ways over the past 30 years. Before the advent of fluoroscopically controlled in-situ pinning, treatment methods such as open epiphysiodesis and spica cast application had been difficult and morbid. Indeed, in-situ pinning was a major advance that at once led to improved outcomes. However, in-situ treatment does not address any residual deformity in the proximal femur. It is now accepted that residual proximal femoral deformity does cause femoroacetabular impingement, which may lead to limited hip ROM, gait disturbance, and osteoarthritis. The problem that remains is how best to treat this residual deformity, when to treat it, and through which surgical technique. Where Do We Need To Go?

Cementless Total Hip Arthroplasty in Hip Dysplasia with an Extensively Porous-Coated Cylindrical Stem Modified for Asians: A 12-Year Follow-Up Study

Long-term outcomes of primary cementless total hip arthroplasty were examined for 198 hips of Asian patients with developmental dysplasia of the hip. AML stems were modified for patients’ relatively small physique. Stable fixation was achieved despite various proximal femoral deformities. At follow up (mean 12.1 years), radiographs demonstrated fixation in all hips, with 100% stem survivorship. Radiographic changes revealed that the severity of stress-shielding was mild in 55% of hips, moderate in 26%, and severe in 19%. Longer follow up is needed to determine whether these changes will develop into clinical manifestations. A distal fixation stem can be a useful reconstruction option when application of a proximal fixation stem in primary total hip arthroplasty is difficult for various reasons.

What Is the Association Between Sports Participation and the Development of Proximal Femoral Cam Deformity?

Background: Femoroacetabular impingement (FAI) is recognized as a common cause of hip pain and intra-articular disorders in athletes. Studies have suggested a link between participation in athletics during adolescence and the development of cam-type deformities of the proximal femoral head-neck junction. Purpose: To investigate the association of sporting activity participation during adolescence and the development of cam deformity. Study Design: Systematic review. Methods: The PubMed, EMBASE, and Cochrane databases were searched to identify potential studies. s and manuscripts (when applicable) were independently reviewed by 2 reviewers. Nine studies met the inclusion criteria, including 8 studies that compared the prevalence of cam deformity in athletes with that in controls and 3 studies that compared the prevalence of cam deformity before and after physeal closure (2 with both). A meta-analysis was performed with pooling of data and random-effects modeling to compare rates of cam deformity between athletes and controls. Results: High-level male athletes are 1.9 to 8.0 times more likely to develop a cam deformity than are male controls. The pooled prevalence rate (by hip) of cam deformity in male athletes was 41%, compared with 17% for male controls. The pooled mean alpha angle among male athletes was 61°, compared with 51° for male controls. Conclusion: Males participating in specific high-level impact sports (hockey, basketball, and possibly soccer) are at an increased risk of physeal abnormalities of the anterosuperior head-neck junction that result in a cam deformity at skeletal maturity.

Does surgical hip dislocation and periacetabular osteotomy improve pain in patients with Perthes-like deformities and acetabular dysplasia?

Patients with symptomatic residual Perthes-like deformities may present with a combination of structural abnormalities including a large aspheric femoral head, short and wide femoral neck, high greater trochanter, and acetabular dysplasia. Sometimes, the hip is further compromised by concurrent symptomatic femoroacetabular impingement (FAI) (proximal femoral deformities) and structural instability (acetabular dysplasia). We therefore sought to characterize (1) the intraoperative findings; (2) radiographic correction; and (3) early patient-reported outcomes, complications, and failures of treating complex Perthes-like hip deformities with combined surgical dislocation and periacetabular osteotomy (PAO). We performed 694 hip preservation procedures between November 2006 and August 2010. Of these, 46 had residual Perthes-like hip deformities, defined as proximal deformity consistent with residual Perthes and a history of Perthes disease or treatment of pediatric hip dysplasia. Of these, we report on 16 patients (16 hips) with residual Perthes-like hip deformities and associated acetabular dysplasia (structural instability, defined as radiographic evidence of acetabular dysplasia with intraoperative confirmation of instability). These 16 patients were treated with a combined surgical hip dislocation to comprehensively address intraarticular and extraarticular sources of FAI and PAO to address structural instability and were analyzed at a minimum 24-month followup (median, 40 months; range, 24-78 months). No patients in this series were lost to followup. Ten patients' hips had previous surgical treatment, including six with previous osteotomy. Operative findings were extracted from standardized prospectively collected intraoperative data collection forms. Radiographic correction was evaluated with established methods (lateral center-edge angle, anterior center-edge angle, acetabular inclination, center-to-trochanter distance) and clinical outcomes were measured with the modified Harris hip score (mHHS) as well as by prospectively recorded data on patient complications and followup. Acetabular labrochondral abnormalities included labral hypertrophy in all hips and labral and/or articular cartilage lesions requiring treatment in 13 hips. Radiographic analysis demonstrated consistent radiographic correction. The median preoperative mHHS improved from 64 to 92 at a median followup of 40 months (p < 0.001). Fourteen patients (14 hips) had a good or excellent clinical result. Two patients (two hips) were classified as failures based on mHHS less than 70 (n = 1) or conversion to total hip arthroplasty (n = 1). Combined surgical hip dislocation and PAO provides major deformity correction in Perthes-like hip deformities with associated acetabular dysplasia. Early clinical results suggest this technique is safe and effective. Long-term studies are needed to determine if improved long-term outcomes are associated with comprehensive deformity correction.

Total Hip Arthroplasty Using the S-ROM-A Prosthesis for Anatomically Difficult Asian Patients.

Background. The S-ROM-A prosthesis has been designed for the Asian proximal femur with a small deformed shape and narrow canal. In this study, the clinical and radiological results using the S-ROM-A prosthesis for Japanese patients with severe deformity due to dysplasia and excessive posterior pelvic tilt were examined. Methods. 94 hips were followed up for a mean of 55 months, with a mean age at surgery of 61 years. The primary diagnoses were 94 coxarthritis cases, including 51 dysplasia and 37 primary OA, 1 avascular necrosis, 2 traumatic arthritis, and 3 Perthes disease. Thirty-one hips had been treated with osteotomy of the hip joints. Preoperative intramedullary canal shapes were stovepipe in 23 hips, normal in 51 hips, and champagne-flute in 5 hips. The maximum pelvic inclination angle was 56°. Results. The mean JOA score improved from 46 points preoperatively to 80 points at final follow-up. On radiological evaluation of the fixation of the implants according to the Engh classification, 92 (97%) hips were classified as “bone ingrown fixation.” Conclusion. In primary THA, using the S-ROM-A prosthesis for Asian patients with proximal femoral deformity, even after osteotomy and with posterior pelvic tilt, provided good short- to midterm results.

Fibrous dysplasia of femur, treated with fibular bone graft

Background: Fibrous dysplasia is a benign bony lesion managed surgically with curettage, bone grafting, and, in some cases, internal fixation. Aims: Study result of cortical bone grafting with fibular strut graft in patient of symptomatic dysplastic lesion without varus deformity of proximal femur. Case Report: A 25-year-old female presented with pain in left hip for 3 months which increased in intensity during walking. Clinically there was no swelling or deformity and tenderness. Range of hip joint movement was normal. The patients had no endocrine disturbances. X-rays of left proximal femur showed radiolucent cystic area involving trochanter, neck, and 30% head at postero-inferior aspect. No pathological fracture was seen. Image showed homogeneous loss of the normal trabecular pattern, with a ground-glass appearance caused by fibrous dysplasia. Patient underwent dual autogenous non-vascularized fibular strut grafts. The dual fibular graft was used as a bridge in the dysplastic lesion in femoral neck and it was securely anchored to the head of femur as well as lateral femoral cortex. The fibular graft was providing excellent structural support without any need for any form of internal fixation. At routine follow-up at 8 months, patient was found ambulating at her own without any substantial pain at the hip joint. Conclusion: For carefully selected patients (symptomatic dysplastic lesion without varus deformity of proximal femur) cortical bone grafting with fibular strut graft is an excellent procedure which provide strong structural support to biomechanically weakened bone.

Treatment of coxa vara utilizing an external fixator

Background Valgus subtrochanteric osteotomy is the gold standard in the surgical treatment of coxa vara. Nevertheless, there has been no consensus on the method of fixation and osteotomy details. In the literature, there are few reports on using rigid internal fixation methods that preclude the need for postoperative immobilization. Patients and methods In this study, 15 hips of 13 patients with the diagnosis of developmental coxa vara underwent subtrochanteric osteotomy with stabilization using an external fixator. Results All osteotomies achieved the planned correction angle, and all osteotomies healed primarily except in one case. Radiographic analysis revealed an improvement in Hilgenreiner's epiphyseal angle and neck-shaft angle. Conclusion This technique proved to be safe and effective in the treatment of proximal femoral deformity associated with coxa vara and limb length discrepancy. It has potential advantages over commonly used open techniques and provides an available alternative to currently applied methods used for fixation of proximal femoral osteotomies.

Fibrous dysplasia of the proximal femur: surgical management options and outcomes.

PurposeThe management of proximal femoral deformity in fibrous dysplasia (FD) is a challenge to the orthopaedic surgeon. The purpose of this study was to analyze the various presentations of FD of proximal femur and the results of the various treatment modalities for the same.MethodsThis is a retrospective cohort study of 23 patients (24 femora) with FD who underwent surgery for the proximal femur. The study sample included 14 males, nine females. Ten patients had a monostotic disease, eight patients had polyostotic disease, and five patients had McCune-Albright syndrome.ResultsGroup 1: shepherd crook deformity—included five patients who underwent femoral neck osteotomy. Four patients had intramedullary (IM) nailing with neck cross-pinning and all patients showed union. One patient was stabilized with external fixation, which failed. Group 2: nine patients (ten femora) presented with frank pathological fracture. Nine underwent fixation with IM nailing, one with locking plate and screws. Three patients had to undergo more than one procedure and all fractures showed good union. Group 3: nine patients who presented with bone cyst and pain. All patients underwent biopsy; four of them had curettage with bone graft.ConclusionShepherd crook deformity can be treated by a well-planned osteotomy and fixation with intramedullary implants with neck cross-pinning. Frank pathological fractures fixation with an intramedullary nail has excellent results even if not accompanied by resolution of the fibrodysplastic lesion. More than one procedure may be required. External fixation is not an optimal choice for fixation of femoral osteotomies in FD.

Relative femoral neck lengthening improves pain and hip function in proximal femoral deformities with a high-riding trochanter.

Complex proximal femoral deformities, including an elevated greater trochanter, short femoral neck, and aspherical head-neck junction, often result in pain and impaired hip function resulting from intra-/extraarticular impingement. Relative femoral neck lengthening may address these deformities, but mid-term results of this approach have not been widely reported. Do patients who have undergone relative femoral neck lengthening show (1) less hip pain and greater function; (2) improved radiographic parameters; (3) significant complications requiring subsequent surgery; and (4) progression of osteoarthrosis (OA) or conversion to total hip arthroplasty (THA) at mid-term followup? We retrospectively reviewed 40 patients (41 hips) with isolated relative femoral neck lengthening between 1998 and 2006 with sequelae of Legg-Calvé-Perthes disease (38 hips [93%]), slipped capital femoral epiphysis (two hips [5%]), and postseptic arthritis (one hip [2%]). During this time, the general indications for this procedure included a high-riding greater trochanter with a short femoral neck with abductor weakness and symptomatic intra-/extraarticular impingement. Mean patient followup was 8 years (range, 5-13 years), and complete followup was available in 38 patients (39 hips [95%]). We evaluated pain and function with the impingement test, limp, abductor force, Merle d'Aubigné-Postel score, and range of motion. Radiographic parameters included trochanteric height, alpha angle, and progression of OA. Subsequent surgeries, complications, and conversion to THA were summarized. The proportion of positive anterior impingement tests decreased from 93% (38 of 41 hips) preoperatively to 49% (17 of 35 hips) at latest followup (p = 0.002); the proportion of limp decreased from 76% (31 of 41 hips) to 9% (three of 35 hips; p < 0.001); the proportion of normal abductor strength increased from 17% (seven of 41 hips) to 91% (32 of 35 hips; p < 0.001); mean Merle d'Aubigné-Postel score increased from 14 ± 1.7 (range, 9-17) to 17 ± 1.5 (range, 13-18; p < 0.001); mean internal rotation increased to 25° ± 15° (range, 0°-60°; p = 0.045), external rotation to 32° ± 14° (range, 5°-70°; p = 0.013), and abduction to 37° ± 13° (range, 10°-50°; p = 0.004). Eighty percent of hips (33 of 41 hips) showed normal trochanteric height; alpha angle improved to 42° ± 10° (range, 27°-90°). Two hips (5%) had subsequent surgeries as a result of lack of containment; four of 41 hips (10%) had complications resulting in reoperation. Fourteen of 35 hips (40%) showed progression of OA; four of 40 hips (10%) converted to THA. Relative femoral neck lengthening in hips with combined intra- and extraarticular impingement results in reduced pain, improved function, and improved radiographic parameters of the proximal femur. Although lack of long-term complications is gratifying, progression of OA was not prevented and remains an area for future research.

Hip contact force in presence of aberrant bone geometry during normal and pathological gait.

Children with cerebral palsy (CP) often present aberrant hip geometry, specifically increased femoral anteversion and neck-shaft angle. Furthermore, altered gait patterns are present within this population. We analyzed the effect of aberrant femoral geometry, as present in CP subjects, on hip contact force (HCF) during pathological and normal gait. We ran dynamic simulations of CP-specific and normal gait using two musculoskeletal models (MSMs), one reflecting normal femoral geometry and one reflecting proximal femoral deformities. The combination of aberrant bone geometry and CP-specific gait characteristics reduced HCF compared to normal gait on a CP subject-specific MSM, but drastically changed the orientation of the HCF vector. The HCF was orientated more vertically and anteriorly than compared to HCF orientation during normal gait. Furthermore, subjects with more pronounced bony deformities encountered larger differences in resultant HCF and HCF orientation. When bone deformities were not accounted for in MSMs of pathologic gait, the HCF orientation was more similar to normal children. Thus, our results support a relation between aberrant femoral geometry and joint loading during pathological/normal gait and confirm a compensatory effect of altered gait kinematics on joint loading.

A semi-automated method for measuring femoral shape to derive version and its comparison with existing methods.

The measurement of femoral version is important in surgical planning of derotational osteotomies particularly for patients with proximal femoral deformity. It is, however, difficult to measure version accurately and differences of 10° to 15° have been found between repeated measurements. The aim of this work was first to develop a method of measuring femoral version angle where the definition of the neck axis is based on the three-dimensional point cloud making up the neck, second to automate many of the processes involved thus reducing the influence of human error and third to ensure the method could run on freely available software suitable for most computer platforms. A CT scan was performed on 44 cadaveric femurs to generate point clouds of the femoral surfaces. The point clouds were then analysed semi-automatically to determine femoral version angle between a neck axis defined by the bone surface points belonging only to the neck and a femoral condylar axis. The results from the neck fitting method were compared against three other methods typically used in the clinic (Murphy, Reikeras and Lee methods). Version angle measured by the new method gave 19.1° ± 7.3° (mean ± standard deviation) for the set of cadaveric femurs, 3.5° lower than the Murphy method and 6.8° and 11.0° higher than the Reikeras and Lee 2D methods respectively. The results demonstrate a method of measuring femoral version angle incorporating a high level of automation running on free software.

Proximal femoral deformity favors hip extension action and impairs pelvic stability during gait: A simulation study using MRI-based musculoskeletal models

Proximal femoral deformity favors hip extension action and impairs pelvic stability during gait: A simulation study using MRI-based musculoskeletal models

The Use of a Cementless Tapered Stem in Young Patients Affected of Secondary Hip Arthritis

Introduction: The Wagner cone stem was designed for uncemented hip arthroplasty in difficult proximal femoral conditions or femoral deformities. The most common indications for the use of this stem are secondary hip arthritis due to developmental hip dysplasia, septic arthritis or congenital malformations. We present a case series of patients that underwent hip arthroplasty with the use of a Wagner cone stem. Materials and methods: A retrospective chart review of 17 patients (15 women and 2 men) was performed with a mean age of 39 (25-62). Clinical evaluation was rated with the Merle DAubigne score. Radiographic evaluation consisted in antero posterior and axial views of the hip. One patient was operated bilaterally, with a total of 18 hips operated, and mean follow up of 8 years (5-12).

Antegrade rigid nailing through the tip of the greater trochanter for pediatric femoral shaft fractures

The aim of this work was to evaluate the results of rigid nailing of pediatric femoral shaft fractures inserted antegrade through the tip of the greater trochanter. Twenty-three femoral shaft fractures in 23 children were fixed with rigid interlocking nails inserted through the tip of the greater trochanter at Mansoura Emergency Hospital in the period between June 2009 and August 2011. The average age of the patients at the time of injury was 12.6 years (range 9.2-15 years). The final follow-up radiographs were assessed for evidence of avascular necrosis (AVN) of the femoral head and any deformity of the proximal femur, the neck-shaft angle, the articulotrochanteric distance, and the femoral neck diameter. Patients were followed to a mean period of 31 months (range from 25 to 36 months) postoperatively. All fractures united in a range of 9 weeks (from 8 to 13 weeks) with no limb length discrepancy more than 2 cm and no clinically evident rotation in either direction; no case had a vascular necrosis of the femoral head or significant proximal femoral deformity by the final follow-up. Fixation of fractures of the shaft of the femur in children with rigid interlocking nails inserted through the tip of the greater trochanter is a rigid way for fixation controlling rotation and length. It is a safe technique without causing AVN of the femoral head or proximal femoral deformity.

Anatomic Footprint of the Direct Head of the Rectus Femoris Origin: Cadaveric Study and Clinical Series of Hips After Arthroscopic Anterior Inferior Iliac Spine/Subspine Decompression

The purposes of this study were to define the anatomy of the anterior inferior iliac spine (AIIS) and its relation to the footprint of the rectus femoris tendon and to evaluate on the clinical outcomes after AIIS/subspine decompression. The rectus origin was dissected and detached in 11 male cadaveric hips with a mean age of 54.3 ± 14.3 years (range, 33 to 74 years). The proximal-distal and medial-lateral extent of the footprint and its relation to the AIIS and acetabular rim were evaluated, with the 12-o'clock position defined as directly lateral at the insertion of the indirect head of the rectus tendon and the 1- to 6-o'clock positions defined as anterior acetabular positions. To assess the safety and efficacy of subspine decompression for AIIS deformity, clinical correlation of a series of 163 AIIS decompressions (mean age, 27.8 years; age range, 14 to 52 years) performed from January 2011 to January 2012 was completed, and outcome scores, strength deficits, and ruptures were assessed by manual muscle testing and postoperative radiographs. All patients presented with symptomatic FAI with proximal femoral and/or acetabular deformity and type 2 (131 hips) or type 3 (32 hips) AIIS morphology as defined by Hetsroni et al. The mean proximal-distal and medial-lateral distances for the rectus origin footprint were 2.2 ± 0.1 cm (range, 2.1 to 2.4 cm) and 1.6 ± 0.3 cm (range, 1.2 to 2.3 cm), respectively. There was a characteristic bare area at the anteromedial AIIS. On the clock face, the lateral margin (1-o'clock to 1:30 position) and medial margin (2-o'clock to 2:30 position) of the AIIS and the indirect head of the rectus (12 o'clock) were consistent for all specimens. In the clinical series, 163 AIIS decompressions were performed for symptomatic subspine impingement. The mean modified Harris Hip Score was 63.1 points (range, 21 to 90 points) preoperatively compared with 85.3 points (range, 37 to 100 points) at a mean follow-up of 11.1 ± 4.1 months (range, 6 to 24 months) (P < .01). Short Form 12 scores improved significantly from a mean of 70.4 (range, 34 to 93) preoperatively to a mean of 81.3 (range, 31 to 99) postoperatively (P < .01). The mean pain score on a visual analog scale also improved significantly from a mean of 4.9 (range, 0.1 to 8.6) preoperatively to a mean of 1.9 (range, 0 to 7.8) postoperatively (P < .01). The mean alpha angle improved from 61.5° (range, 35° to 90°) preoperatively to 49° (range, 35° to 63°) postoperatively on anteroposterior radiographs and from 71° (range, 45° to 90°) preoperatively to 44.3° (range, 37° to 60°) postoperatively on lateral radiographs. No short- or long-term hip flexion deficits or rectus femoris avulsions were noted with up to 2 years' follow-up. The origin of the rectus femoris tendon is broad on the AIIS and protective against direct head detachment with subspine decompression. This broad origin and consistent bare area anteromedially on the AIIS can be readily used by surgeons to perform a safe AIIS resection in cases of symptomatic impingement. Arthroscopic subspine decompression in addition to osteoplasty for symptomatic cam- and/or pincer-type FAI deformities can reliably improve outcome scores without significant hip flexion deficits or AIIS/rectus femoris avulsions. The direct head of the rectus tendon has a broad insertion on the AIIS, and an area devoid of tendon provides a "safe zone" for subspine decompression in cases of symptomatic AIIS impingement.