Preoperative Dynamic Hip Examination Under Fluoroscopic Guidance Enhances the Understanding of Femoroacetabular Impingement Pathology and Treatment Planning.

PURPOSE: To review the relative accuracy of preoperative magnetic resonance imaging (MRI) and fluoroscopically guided examination-under-sedation (EUS) findings and to explore the validity of the anterior acetabular sector angle (AASA) as a radiologic MRI-based marker of anterior acetabular coverage in pincer-type impingement. METHODS: A cohort of 150 consecutive patients undergoing primary hip arthroscopy for femoroacetabular impingement (FAI) in 2018 to 2019 was reviewed. The inclusion criteria were pure FAI unilateral symptomatic pathology and the availability of complete data sets (MRI, EUS, and intraoperative records). Preoperative MRI and EUS findings were compared with gold-standard intraoperative arthroscopic findings, specifically evaluating the alpha angle in the presence of cam lesions, AASA in the presence of pincer lesions, as well as soft-tissue lesions. An alpha angle greater than 50° and an AASA greater than 65° were deemed pathologic. RESULTS: The patient cohort included 78 women and 72 men with an average age of 38 years (range, 18-53 years). Intraoperatively, pincer lesions were present in 20% of patients; cam lesions, 26%; and mixed impingement, 54%. MRI versus EUS correctly identified pincer lesions in 36% versus 89% of cases and identified cam lesions in 44% versus 77% of cases. MRI findings characterizing labral tears and articular cartilage pathology were accurate in 80% and 10% of cases, respectively. Although there was no difference in the AASA between pure pincer- and mixed-type impingements (62° and 63°, respectively; P = .62), there was a statistically significant difference in reported AASA values between pure cam-type impingement and impingement involving the presence of pincer lesions (57° and 63°, respectively; P = .03). Furthermore, 31% of patients with intraoperatively identified pincer lesions had an AASA of 60° to 65°. CONCLUSIONS: Fluoroscopic EUS is accurate in characterizing FAI pathology. In addition, MRI is useful to diagnose or rule out non-FAI pathology, ascertain labral pathology, and outline hip alignment. These methods of preoperative planning are complementary. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Photoelastic comparison of strains in the underlying glenoid with metal-backed and all-polyethylene implants.

An alteration in the stress and strain environment following arthroplasty is believed to lead to bone remodeling, which can trigger implant loosening and subsequent failure. Bone remodeling, while well-studied in hip arthroplasty, has received less attention in total shoulder replacement. This study examines differences in strain states between intact glenoids and following replacement with an uncemented metal backed keeled component and a cemented all polyethylene pegged component with the same articular geometry, using the photoelastic method. Strain measurements were taken in glenoids before and after implantation under 4 loading conditions corresponding to 4 abduction angles: 0 degrees, 30 degrees, 60 degrees, and 90 degrees. Shear strains increased at most locations following reconstruction with both of the implants. Uncemented, keeled metal backed implants produced areas of higher cortical shear strains compared to cemented, all PE pegged implants.

Effect of low intensity pulsed ultrasound on healing of an ulna defect filled with a bone graft substitute.

A 1.5 cm unilateral rabbit ulna defect model was performed in 18 adult NZ white rabbits. The defects were filled with a beta-tricalcium phosphate bone graft substitute (JAX TCP). The surgical site in half the animals was treated daily with 20 min of low intensity pulsed ultrasound (LIPUS). Animals were sacrificed at 4 weeks (n = 3 per group) or 12 weeks (n = 6 per group) following surgery for radiographic and histologic endpoints. Radiography revealed some resorption of the JAX TCP by 12 weeks in the control and LIPUS treated groups. LIPUS treatment did not accelerate this resorption. Some new bone formation was noted in the control groups at the defect margins while little bone formed in the center of the defect at 4 and 12 weeks. In contrast, radiographs revealed more new bone at 4 and 12 weeks in the LIPUS treated animals throughout the section. Bone mineral density (DEXA) revealed a statistically significant difference at 4 weeks with LIPUS while no differences were found at 12 weeks. Histology of the LIPUS treated sections demonstrated new woven bone formation on and between the JAX TCP bone graft substitute particles across the defect. VEGF expression was increased with LIPUS treatment at 4 weeks and remained elevated at 12 weeks compared with controls. CBFA-1 expression levels were elevated with LIPUS treatment at both time points. LIPUS treatment increased bone formation in ulna defect healing with a beta-tricalcium phosphate bone graft substitute.

The influence of ambient theater temperature on cement setting time.

We have prospectively recorded ambient operating theater temperature from 186 total knee arthroplasties and the time taken for the cement to set at implantation. The majority of cases used Antibiotic Simplex cement (n = 131), and the rest, Simplex with tobramycin (n = 55). Set time was defined as when a no. 15 scalpel could not indent the cement surface at either the femoral or tibial interface. There was a reasonable negative correlation between temperature and setting time (Antibiotic Simplex: Pearson correlation coefficient, R = -0.674; Simplex with tobramycin: R = -0.655). There was also a considerable variation of setting time at any given theater temperature. There is an inverse relationship between ambient theater temperature and the setting time for Simplex cement, and surgeons should be aware that the setting time can vary considerably. Their operative protocol should take this into account.

Oxford medial unicompartmental arthroplasty for focal spontaneous osteonecrosis of the knee.

BACKGROUND: Spontaneous osteonecrosis of the knee (SONK) is a distinct clinical condition occurring in patients without any associated risk factors. There is controversy as to the best method of treatment, and the available literature would suggest that patients with SONK have a worse outcome than those with primary osteoarthrosis when arthroplasty is performed. We assessed the outcome of medial unicompartmental knee arthroplasty (UKA) using the Oxford prosthesis for end-stage focal spontaneous osteonecrosis of the knee (SONK; Ahlbäck grades III and IV). PATIENTS AND METHODS: We assessed 29 knees (27 patients) with spontaneous osteonecrosis of the knee using the Oxford Knee Score. 26 knees had osteonecrosis of the medial femoral condyle and 3 had osteonecrosis of the medial tibial plateau. All had been operated on using the Oxford Medial Unicompartmental Knee Arthroplasty (UKA). This group was compared to a similar group (28 knees, 26 patients) who had undergone the same arthroplasty, but because of primary osteoarthrosis. Patients were matched for age, sex and time since operation. The mean length of follow-up was 5 (1-13) years. RESULTS: There were no implant failures in either group, but there was 1 death (from unrelated causes) 9 months after arthroplasty in the group with osteonecrosis. The mean Oxford Knee Score in the group with osteonecrosis was 38, and it was 40 in the group with osteoarthrosis. INTERPRETATION: Use of the Oxford Medial UKA for spontaneous focal osteonecrosis of the knee is reliable in the short to medium term, and gives results similar to those obtained when it is used for patients with primary osteoarthrosis.

The clinical relevance of Tarlov cysts.

OBJECTIVE: The sacral perineural cyst was first described by Tarlov in 1938 as an incidental finding at autopsy. There are very few data in the literature regarding the role of Tarlov cysts in causing symptoms, however. Most studies report low numbers, and consequently, the recommendations for treatment are vague. Our aim, therefore, is to present further detail regarding the clinical relevance of Tarlov cysts and to identify whether or not they are a cause of lumbosacral spinal canal stenosis symptoms. METHODS: Over a 5-year period, 3535 patients underwent magnetic resonance imaging (MRI) scan for lumbosacral symptoms. Fifty-four patients were identified as having Tarlov cysts, and their clinical picture was correlated with the findings on MRI. RESULTS: The majority of Tarlov cysts (n = 38) cannot be held responsible for patients' symptoms and are clinically unimportant. However, we encountered several patients in whom Tarlov cysts (n = 9) occurred at the same level as another pathology. In these cases, the cyst itself did not require any specific therapy; treatment was directed at the other pathology, and uneventful symptom resolution occurred. A smaller subgroup of cysts (n = 7) are the main cause of patients' symptoms and may require specific treatment to facilitate local decompression. CONCLUSIONS: The majority of Tarlov cysts are incidental findings on MRI. Where confusion exists as to the clinical relevance of a Tarlov cyst, treatment of the primary pathology (ie, non-Tarlov lesion) is usually sufficient. Tarlov cysts may, however, be responsible for a patient's symptoms; possible mechanisms by which this may occur and treatment strategies are discussed.