Does Femoroacetabular Impingement Cause Hip Instability? A Systematic Review.

PURPOSE: To determine whether femoroacetabular impingement (FAI) is associated with hip instability. METHODS: A systematic search examining FAI and hip instability was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Clinical and basic science studies were included. Instability had to be documented with either a clinical or imaging examination. Studies were excluded if they did not define diagnostic criteria for FAI, involved prosthetic hips, were not in English, were review articles, or reported Level V evidence (case reports, expert opinion). Rates of FAI morphologic features in patients with documented hip instability were determined. Mechanisms and rates of FAI-induced hip subluxation were examined in basic science studies. RESULTS: The search yielded 1,630 relevant studies. Seven studies (4 clinical and 3 basic science) met inclusion criteria. Four studies investigated an association between FAI and hip instability in 92 patients with an average age of 31 years. Seventy-six patients experienced frank dislocations and 16 experienced posterior subluxation events. The prevalence of FAI was documented in 89 patients with hip instability. The rates of cam and pincer morphologic characteristics were 74% and 64%, respectively. The average lateral center edge angle and prevalence of acetabular retroversion were 30° and 70%, respectively (n = 76 patients). All 3 basic science studies had real-time visualization of FAI-induced hip subluxations. CONCLUSIONS: High rates of FAI morphologic characteristics are present in patients with hip instability. FAI morphologic characteristics may predispose the hip to instability through anatomic conflict caused by pincer or cam lesions (or both) levering the femoral head posteriorly. LEVEL OF EVIDENCE: Level IV, systematic review of Level III, Level IV, and non-clinical studies.

Cumulative Radiation Exposure to Patients Undergoing Arthroscopic Hip Preservation Surgery and Occupational Radiation Exposure to the Surgical Team.

PURPOSE: To quantify cumulative radiation exposure in patients undergoing arthroscopic hip preservation surgery and occupational exposure to operating room (OR) personnel during such surgery; a secondary objective of this study was to identify factors affecting radiation exposure in patients undergoing hip arthroscopy. METHODS: Radiation exposure from all preoperative and intraoperative imaging studies was determined for 52 patients undergoing hip arthroscopy. Cumulative and effective radiation doses were calculated and correlated with pathology and body mass index (BMI). Badge dosimeters were worn by OR personnel to measure cumulative occupational exposure. A highly sensitive portable ion chamber was used to evaluate the radiation scatter during surgery performed on a high-BMI patient and a low-BMI patient to reflect a "worst-case scenario" and "best-case scenario," respectively. RESULTS: Forty-three patients underwent procedures for femoroacetabular impingement (FAI) and 9 underwent procedures for soft-tissue pathologies (ST). The median cumulative exposure was 8.6 mGy and 5.0 mGy for FAI patients and ST patients, respectively (P = .01). The cumulative effective radiation dose was 490 mrem and 350 mrem for FAI patients and ST patients, respectively (P = .47). BMI significantly correlated with cumulative exposure (P = .0004) and trended toward significance with cumulative effective dose (P = .073). OR staff cumulative occupational exposure was low (9 mrem for the surgeon). Ion chamber data showed that increasing patient BMI resulted in increased occupational exposure. CONCLUSIONS: The median cumulative effective radiation dose to patients undergoing arthroscopic hip preservation surgery is 490 mrem and results in an excess lifetime risk of death from cancer of 0.025%. Greater BMI correlates with increased cumulative radiation exposure and may increase risk to OR personnel. Occupational exposure to the surgical team from hip arthroscopy ranges from 7 to 9 mrem per 50 hip arthroscopies (+0.0005% excess lifetime risk of death from cancer). LEVEL OF EVIDENCE: Level IV, diagnostic.

A nondestructive, reproducible method of measuring joint reaction force at the distal radioulnar joint.

PURPOSE: To develop a nondestructive method of measuring distal radioulnar joint (DRUJ) joint reaction force (JRF) that preserves all periarticular soft tissues and more accurately reflects in vivo conditions. METHODS: Eight fresh-frozen human cadaveric limbs were obtained. A threaded Steinmann pin was placed in the middle of the lateral side of the distal radius transverse to the DRUJ. A second pin was placed into the middle of the medial side of the distal ulna colinear to the distal radial pin. Specimens were mounted onto a tensile testing machine using a custom fixture. A uniaxial distracting force was applied across the DRUJ while force and displacement were simultaneously measured. Force-displacement curves were generated and a best-fit polynomial was solved to determine JRF. RESULTS: All force-displacement curves demonstrated an initial high slope where relatively large forces were required to distract the joint. This ended with an inflection point followed by a linear area with a low slope, where small increases in force generated larger amounts of distraction. Each sample was measured 3 times and there was high reproducibility between repeated measurements. The average baseline DRUJ JRF was 7.5 N (n = 8). CONCLUSIONS: This study describes a reproducible method of measuring DRUJ reaction forces that preserves all periarticular stabilizing structures. This technique of JRF measurement may also be suited for applications in the small joints of the wrist and hand. CLINICAL RELEVANCE: Changes in JRF can alter native joint mechanics and lead to pathology. Reliable methods of measuring these forces are important for determining how pathology and surgical interventions affect joint biomechanics.

Distal Radioulnar Joint Reaction Force Following Ulnar Shortening: Diaphyseal Osteotomy Versus Wafer Resection.

PURPOSE: To compare how ulnar diaphyseal shortening and wafer resection affect distal radioulnar joint (DRUJ) joint reaction force (JRF) using a nondestructive method of measurement. Our hypothesis was that ulnar shortening osteotomy would increase DRUJ JRF more than wafer resection. METHODS: Eight fresh-frozen human cadaveric upper limbs were obtained. Under fluoroscopic guidance, a threaded pin was inserted into the lateral radius orthogonal to the DRUJ and a second pin was placed in the medial ulna coaxial to the radial pin. Each limb was mounted onto a mechanical tensile testing machine and a distracting force was applied across the DRUJ while force and displacement were simultaneously measured. Data sets were entered into a computer and a polynomial was generated and solved to determine the JRF. This process was repeated after ulnar diaphyseal osteotomy, ulnar re-lengthening, and ulnar wafer resection. The JRF was compared among the 4 conditions. RESULTS: Average baseline DRUJ JRF for the 8 arms increased significantly after diaphyseal ulnar shortening osteotomy (7.2 vs 10.3 N). Average JRF after re-lengthening the ulna and wafer resection was 6.9 and 6.7 N, respectively. There were no differences in JRF among baseline, re-lengthened, and wafer resection conditions. CONCLUSIONS: Distal radioulnar joint JRF increased significantly after ulnar diaphyseal shortening osteotomy and did not increase after ulnar wafer resection. CLINICAL RELEVANCE: Diaphyseal ulnar shortening osteotomy increases DRUJ JRF, which may lead to DRUJ arthrosis.

Total Knee Arthroplasty in the Osteoporotic Tibia: A Biomechanical Evaluation of the Role of Stem Extensions and Cementing Techniques.

INTRODUCTION: Poor functional outcomes and aseptic loosening increase when total knee arthroplasty is performed on osteoporotic patients. This biomechanical study evaluated the effect of stem extension on the stability of tibial fixation using different cementing techniques. METHODS: A standard design tibial tray was implanted in a replica of a male osteoporotic tibia. Twenty-four implantations were performed using three variations of implant and cementing, and then mounted on a material testing machine load frame at 500 cycles of multiaxial loading simulating walking. The three-dimensional components of tray-tibia micromotion were measured. RESULTS: The primary implant total interface motion with surface cementing was 25.9 µm ± 14.7 µm and 10.6 µm ± 7.6 µm with full cementing (P = 0.001). The three-dimensional motion of fully cemented primary implants with stem extension was 4.4 µm ± 3.9 µm, which represents a decrease in micromotion of 83% in surface cemented primary implants (P < 0.0001) and 58% in the fully cemented components without stem extension (P < 0.009). CONCLUSION: Fully cemented primary implants with stem extensions demonstrated decreased micromotion and should be considered for use in osteoporotic total knee arthroplasty patients.

Antibiotic impregnated total femur spacers: a technical tip.

Simultaneous prosthetic joint infection of ipsilateral hip and knee arthroplasties is often accompanied by significant bone loss and presents a challenging reconstructive problem. Two-stage reconstruction is favored and requires the placement of a total femur spacer, which is not a commercially available device. We describe a surgical technique, reporting on 2 cases in which a customized total femur antibiotic impregnated spacer was created by combining an articulating knee spacer and an articulating hip spacer with a reinforced cement dowel construct connecting the 2 spacers. Custom total femoral spacers are useful in the management of infected femoral megaprostheses and cases with ipsilateral injected hip and knee arthroplasties and severe femoral bone loss.

External fixator immobilization after extensor mechanism reconstruction in total knee arthroplasty.

Extensor mechanism disruption after total knee arthroplasty is a complicated problem that typically requires surgical reconstruction. After extensor mechanism failure, reconstruction is typically indicated to restore active knee extension and provide a stable limb for ambulation. Immobilization of the knee in extension is vital in the initial postoperative period after extensor mechanism reconstruction. We describe a series of 4 patients who underwent extensor mechanism reconstruction followed by external fixator application to maintain the knee extended in the initial postoperative period. Our results have been favorable. However, close follow-up is important to monitor for the development of pin site infections.

Techniques of Force and Pressure Measurement in the Small Joints of the Wrist.

BACKGROUND: The alteration of forces across joints can result in instability and subsequent disability. Previous methods of force measurements such as pressure-sensitive films, load cells, and pressure-sensing transducers have been utilized to estimate biomechanical forces across joints and more recent studies have utilized a nondestructive method that allows for assessment of joint forces under ligamentous restraints. METHODS: A comprehensive review of the literature was performed to explore the numerous biomechanical methods utilized to estimate intra-articular forces. RESULTS: Methods of biomechanical force measurements in joints are reviewed. CONCLUSIONS: Methods such as pressure-sensitive films, load cells, and pressure-sensing transducers require significant intra-articular disruption and thus may result in inaccurate measurements, especially in small joints such as those within the wrist and hand. Non-destructive methods of joint force measurements either utilizing distraction-based joint reaction force methods or finite element analysis may offer a more accurate assessment; however, given their recent inception, further studies are needed to improve and validate their use.

Corrosion and adverse local tissue reaction after total hip arthroplasty with a modular titanium alloy femoral neck.

This report describes a case of mechanically assisted crevice corrosion and secondary adverse local tissue reaction in a patient following a total hip arthroplasty, utilizing a modular neck (bi-modular) femoral component. Radiographic evaluation demonstrated a well-positioned, stable, cementless arthroplasty. Upon further evaluation, the patient had elevated serum cobalt and chromium levels, and magnetic resonance imaging demonstrated a periprosthetic pseudotumor. Corrosion of both the neck-stem and head-neck junctions was suspected. At the time of surgery, the neck-body junction was pristine; however, the head-neck junction of the implant demonstrated severe corrosive wear, a problem that has been reported only once previously with this particular bi-modular implant. This serves as a reminder that any modular junction may be susceptible to corrosion and not all bi-modular designs behave similarly.

Atraumatic Hip Instability.

Atraumatic hip instability is an increasingly recognized source of pain and hip dysfunction. It can result from numerous causes, including femoroacetabular impingement, prior trauma, injury to the capsuloligamentous structures, and idiopathic etiologies. Occult hip instability can be a challenging diagnosis that requires careful attention to, and interpretation of, history, physical examination, and radiographic imaging findings. Iatrogenic hip instability is a potential complication of both open and arthroscopic hip-preserving surgical procedures that can have catastrophic results. Atraumatic hip instability is a pathologic entity that can be successfully addressed with open and arthroscopic procedures.

Incidence of Intracapsular Placement When Inserting Medial Talar Body Schanz Pins: An Anatomic Study.

OBJECTIVES: Medial talar body pins may be inserted to provide points of fixation in the hindfoot when applying external fixators. Because of the proximity to the ankle joint, there is a risk of intracapsular pin placement. We hypothesized that intracapsular placement is common when inserting medial talar body pins. METHODS: Medial talar body pins were inserted in 12 fresh frozen cadaver ankles. Arthrography of each ankle was then performed to determine whether the pin was intracapsular. Each pin was then removed, and fluoroscopy was repeated to evaluate for contrast extravasation from the pin insertion site. The distance from the apex of the talar head to the anterior extent of the ankle capsule was measured to determine a safe area for extracapsular pin placement. RESULTS: Arthrograms of all 12 ankles demonstrated that the pins were intracapsular. After pin removal, there was contrast extravasation from the pin insertion site in all specimens. Contrast was present in the pin tract in all specimens. Mean distance from the talar head to the anterior ankle capsule was 20.95 ± 4.8 mm (range, 12.2-27.3 mm) on the lateral view and 15.5 ± 1.8 mm (range, 12.4-20.0 mm) on the anteroposterior view of the foot. CONCLUSIONS: There is a high rate of intracapsular pin placement when inserting medial talar body pins. Pin placement within the joint capsule risks seeding a sterile joint with bacteria and fistula formation when the pin remains in place for prolonged periods. For this reason, talar body pins should be avoided in temporizing external fixation frames.

The influence of insurance status on access to and utilization of a tertiary hand surgery referral center.

BACKGROUND: The purpose of this study was to systematically examine the impact of insurance status on access to and utilization of elective specialty hand surgical care. We hypothesized that patients with Medicaid insurance or those without insurance would have greater difficulty accessing care both in obtaining local surgical care and in reaching a tertiary center for appointments. METHODS: This retrospective cohort study included all new patients with orthopaedic hand problems (n = 3988) at a tertiary center in a twelve-month period. Patient insurance status was categorized and clinical complexity was quantified on an ordinal scale. The relationships of insurance status, clinical complexity, and distance traveled to appointments were quantified by means of statistical analysis. An assessment of barriers to accessing care stratified with regard to insurance status was completed through a survey of primary care physicians and an analysis of both patient arrival rates and operative rates at our tertiary center. RESULTS: Increasing clinical complexity significantly correlated (p < 0.001) with increasing driving distance to the appointment. Patients with Medicaid insurance were significantly less likely (p < 0.001) to present with problems of simple clinical complexity than patients with Medicare and those with private insurance. Primary care physicians reported that 62% of local surgeons accepted patients with Medicaid insurance and 100% of local surgeons accepted patients with private insurance. Forty-four percent of these primary care physicians reported that, if patients who were underinsured (i.e., patients with Medicaid insurance or no insurance) had been refused by community surgeons, they were unable to drive to our tertiary center because of limited personal resources. Patients with Medicaid insurance (26%) were significantly more likely (p < 0.001) to fail to arrive for appointments than patients with private insurance (11%), with no-show rates increasing with the greater distance required to reach the tertiary center. CONCLUSIONS: Economically disadvantaged patients face barriers to accessing specialty surgical care. Among patients with Medicaid coverage or no insurance, local surgical care is less likely to be offered and yet personal resources may limit a patient's ability to reach distant centers for non-emergency care.